Showing 63 results for Regression
B. Siahsar, A. Rezai,
Volume 3, Issue 3 (10-1999)
Abstract
In order to study the genetic and environmental variability of morphological and phenological characteristics and also to gain a better understanding of the morphological basis of yield variation in soybean, an experiment was conducted at Research Farm, College of Agric., Isfahan University of Technology, in 1996. The experiment was arranged in three augmented designs with 285 lines and 5 control varieties. There were highly significant differences among genotypes for all the characteristics studied. The phenotypic coefficients of variability were greater than the genotypic ones for all the traits although the differences for most of them were small. The highest phenotypic and genotypic coefficients of variation, in order of magnitude, were obtained for number of pods per plant, days to flowering, plant height, height of the lowest pod, and number of lateral branches. Heritability estimates and the percent of genetic improvement for these traits and seed weight were high but for seed yield per plant were low. The lowest coefficients of variability were related to number of seeds per pod and days to germination. The results of stepwise regression analysis indicated that the maximum variation in seed yield could be attributed to the number of pods per plant, number of seeds per pod, and 100-seed weight. Factor analysis in addition to emphasizing the importance of yield components, resulted in four factors which determined 97.34% of yield variation. These factors which were indicators of physiological sink and source, with respect to the traits contained, were named as photosynthetic sink, plant architecture, fixed capital, and weight, respectively. In general, it was concluded that in order to improve soybean cultivars, selection should be in favor of plants with stronger structure, higher number of leaves, nods and pods per plant, and higher seed weights.
F. Noorbakhsh, M. Afyuni,
Volume 4, Issue 1 (4-2000)
Abstract
Field capacity (FC) and permanent wilting point (PWP) are important factors affecting irrigation scheduling and field management. FC and PWP can be estimated from some of the soil physical and chemical properties. Pressure Plate apparatus is usually used for determination of FC and PWP, but this is a time-consuming and laborious procedure besides, the apparatus may not be available in many laboratories. Samples were taken from 23 locations in Isfahan and Chaharmahal Va Bakhtiary provinces in central Iran. Soil texture, organic matter and cation exchange capacity were determined. Soil moisture at FC and PWP of the soils were measured with a pressure plate. Simple and multiple regression analyses were used to study the relationships between FC and PWP with sand, silt, clay, soil organic matter and cation exchange capacity.
Results indicated that FC significantly correlated with sand, organic matter and cation exchange capacity in a stepwise model (r=0.97**). The PWP of soil also correlated significantly with silt, organic matter, and cation exchange capacity in a stepwise model (r=0.95**). Available water capacity (FC-PWP) correlated with sand in a stepwise model (r=0.82**). On the whole, results showed that FC and PWP can be estimated from some soil physical and chemical properties.
R. Amiri, A. Rezai,
Volume 5, Issue 2 (7-2001)
Abstract
In order to evaluate the relationship between SDS-sedimentation value and breadmaking quality of wheat (Triticum aestivum L.), glutenin subunits of different genotypes (foreign and Iranian cultivars) were analyzed by reverse-phase high performance liquid chromatography (RP-HPLC). SDS-sedimentation value was used as an indirect criterion for breadmaking quality.
Correlation coefficients revealed a closer relationship between low molecular weight (LMW) glutenin subunits and variation in SDS-sedimentation value. Principal component analysis confirmed the presence of association between some of the glutenin subunits and SDS-sedimentation value. Based on the stepwise regression analysis, two LMW and four high molecular weight (HMW) peaks (subunits) were selected which accounted for 70.2 and 18.7% of variability in SDS sedimentation values, respectively. On the basis of the results of the stepwise regression analysis, a discriminant function was developed. The great efficiency of discriminant function in correct classification of completely different genotypes (Iranian landraces and cultivars) showed that the observed relationship between glutenin subunits and SDS-sedimentation value has a genetic basis and the effects of LMW and HMW glutenin subunits on SDS-sedimentation value are additive. Therefore, it seems that this method based on more protein components (rather than only on HMW glutenin subunits) can be used to predict breadmaking quality of wheat against many genetic backgrounds.
F. Azizi, A. Rezai, S.m. Maybodi,
Volume 5, Issue 3 (10-2001)
Abstract
In order to investigate the genetic diversity of morphological traits in 121 genotypes of lima, red and pinto beans, and to study the relation between characters, and to get better understanding of factors affecting the interaction between characters by multivariate analysis, an experiment was conducted in 1997 as a simple lattice design at the Research Station of Agricultural College, Isfahan University of Technology.
High variability was observed among genotypes for all characters studied. The phenotypic coefficients of variability were greater than the genotypic ones for all the traits. Among the characters studied seed yield, number of pods per lateral branches and main stem, length of lateral branches and main stem, number of nodes per lateral branches and main stem, 100-seed weight and number of lateral branches had the highest genotypic and phenotypic variability, while days to maturity had the lowest variability. Traits relative to lateral branches were more variable than the same traits in the main stem. Factor analysis for all the genotypes and, separately, for lima, red, pinto, determinate and indeterminate genotypes revealed 4 factors which justified more than 78.4 percent of the total variation. The results of the analysis based on all the genotypes showed that the first factor was mostly correlated to days to maturity, length of main stem and lateral branches, number of nodes per main stem and lateral branches, which was named “vegetative factor”. The second and third factors had the highest correlations with number of pods per main stem and lateral branches, number of seeds per pod in the main stem and branches and 100-seed weight, which were named “yield component factors”. The fourth factor showed the highest correlation with number of lateral branches and was named for this trait. The first and fourth factors were related to vegetative growth characteristics and physiological source. The second and third factors were related to physiological sink. On the basis of stepwise regression analysis, number of pods per lateral branches was the most important component of yield, and number of pods per lateral branches and main stem had the next following ranks. Number of pods per lateral branches and main stem had the highest relationships with yield.
A. Dehdari, M. Mobli, A. Rezai,
Volume 5, Issue 4 (1-2002)
Abstract
In order to determine the relationships among the different traits of onion and to study the direct and indirect effects of these traits on bulb and seed yield, an experiment was conducted in 1998 at the research farm of Isfahan University of Technology. Results showed that phenotypic and genotypic correlations were similar and bulb weight showed the highest and lowest coefficients of correlation with bulb diameter and number of days to emergence, respectively. Results of stepwise regression analysis showed that leaf width at 25% of its length from the neck, leaf length, and leaf dry weight were the best estimators for leaf area bulb diameter, bulb length, plant height and number of days to maturity were the most important determining characters for bulb yield variation. Number of fertilized florets was the best determinator of seed yield and bulb weight, while diameter and volume were the best describing characters for the number of meristems on the basal plate. Path-coefficient analysis revealed that bulb diameter showed the highest direct positive effect on bulb yield and the indirect effect of plant height through bulb diameter on it was of prime importance. Number of fertilized florets per plant and number of inflorescence per plant through the number of fertilized florets showed the highest direct and indirect effects on seed weight, respectively.
M. M. Ghasemi, A. R. Sepaskhah,
Volume 8, Issue 1 (4-2004)
Abstract
The vast pastures and agricultural development plans for dry farming and irrigated farming in Khuzestan Province depend on rain. This requires availability of annual precipitation prediction models to be used in the management decision-making process. In this research, the long-term daily precipitation data from 15 rain gauge stations in the study area were collected for study and a relationship between the early fall season precipitations of 42.5 mm (t42.5) and the annual precipitation was obtained. The results showed that the relationship was an inverse one such that the later the fall precipitation occurred, the greater the annual precipitation would be. To increase the coefficient of determination in the models, climatic variables such as Persian Gulf sea surface temperature and geographical characteristics (longitude, latitude, altitude, and long term mean annual precipitation) were used. Except for the long term mean annual precipitation and altitude, other variables did not increase the coefficient of determination. The final simple model found is as follows: Pa=184.787-1.891t42.5+0.855Pm , R2=0.704 where, Pa is the annual precipitation, t42.5 is the time from beginning of fall season for 42.5 mm of precipitation, and Pm is the long term mean annual precipitation.
S. S. Eslamian, A. Zarei, A. Abrishamchi,
Volume 8, Issue 1 (4-2004)
Abstract
An approach for regional low flow frequency analysis is to use multiple regression techniques for obtaining relationships between low flows with specific return periods and catchments characteristics. In this paper, this method has been used. After single-site frequency analysis for 20 stream gauging stations, homogeneity test was performed. Regional relationships between low flows with return periods 2 , 5 , 10, and 20 years and catchments characteristics were derived.
For this purpose, catchment area, mean elevation, minimum elevation, shape factor, main channel length, length of main chanel from catchment centroid to outlet, forest area, mean annual rainfall, and mean catchment slope as model inputs were examined and cachment area, mean elevation, and mean catchment slope entered to the models. Finally, the mean relative error of models for different return period, 2, 5, 10, and 20 years, was computed 41.1, 41.3, 45.0, 47.2 percent, respectively that in comparison with other studies, it displays smaller errors.
M. Khalili Mahani, B. Hatami, H. Seyedoleslami, A. M. Rezaei, B. Heidari,
Volume 8, Issue 4 (1-2005)
Abstract
Elm leaf beetle were reared under controlled conditions (25± 2 oC, 70± 5%R.H. and 16L: 8D) to determine relationship between biological traits and the number of eggs per female on different hosts and to evaluate correlation between traits. U. carpinifolia, U .c. var. umbraculifera, U. glabra var. pendula and Celtis caucasica were examined as hosts. The biological traits consisted of 1st, 2nd and 3rd larval developmental times first, second, and third larval percent mortality rates prepupal and pupal developmental times male and female longevity and pre-ovipositional period recorded during experiments. The relationships between traits and the number of eggs per female were determined by multiple regression (Foreward selection and stepwise). The correlation between traits was evaluated, too. The results showed that the number of eggs per female were mostly affected by certain special traits such as 2nd and 3rd larval developmental time, pre-ovipositional period and male longevity which are distinct in different hosts and seasons.
J. Mohammadi, S.m. Taheri,
Volume 9, Issue 2 (7-2005)
Abstract
Pedotransfer functions are the predictive models of a certain soil property from other easily, routinely, or cheaply measured properties. The common approach for fitting the pedotransfer functions is the use of the conventional statistical regression method. Such an approach is heavily based on the crisp obervations and also the crisp relations among variables. In the modeling natural systems, like soil, we are dealing with imprecise observations and the vague relations among the variables. Therefore, we need an appropriate algorithm for modeling such a fuzzy structures. In the present study, the fuzzy regression approach was used in order to fit some chemical and physical pedotransfer functions. The optimum regression models with the fuzzy coefficients were obtained for modeling pedotransfer functions. Sensivity analysis was carried out by using the credibility level.
The results indicated that the fuzzy regression might be considered, as a suitable alternative or a complement to the statistical regression, whenever a relationship between variables is imprecise and generally when dealing with the errors due to a vaguness in regression models.
M. J. Nazemosadat, A. Shirvani,
Volume 9, Issue 3 (10-2005)
Abstract
Since the fluctuations of the Persian Gulf Sea Surface Temperature (PGSST) have a significant effect on the winter precipitation and water resources and agricultural productions of the south western parts of Iran, the possibility of the Winter SST prediction was evaluated by multiple regression model. The time series of PGSSTs for all seasons, during 1947-1992, were considered as predictors, and the time series of MSSTs during 1948-1993, as the prrdictand. For the purpose of data reduction and principal components extraction, the principal components analysis was applied. Just the scores of the first four PCs (PC1 to PC4) that accounted for the total variance in predictor field were considered as the input file for the regression analysis. For finding the dependency of each principal component to the first time series of the PGSST, the Varimax rotation analysis was applied. The results have indicated that PC1 to PC4 respectively are the indicator of temperature changes during winter, autumn, Spring and Summer. According to the regression model, the components of PC1, PC2 and PC4 were significant at 5% level. But the components of PC3 was insignificant. The results indicated that the significant variables are held accountable for the 33.5% of the total variance in the winter PGSSTs. It became obvious that for the prediction of the winter PGSST, the PGSST during the winter of the last year has a particular importance. At the next stage, autumn and summer temperature have also a role in prediction of winter PGSST.
S. H. Hosseiniparvar, J. Keramat, M. Kadivar,
Volume 11, Issue 40 (7-2007)
Abstract
This research was carried out to determine the optimum conditions for acidic extraction of gelatine from cattle bones. The effects of different treatments such as pH (1.8 to 2.6), temperature (60 to 80°C) and time (40 to 120minutes) on yield of extraction, gel strength, viscosity and absorption (420 nm) was measured. Coefficients of central composite rotatable design (CCRD) and regression surface response.... (RSREG) were used. The coefficients for yield, gel strength, viscosity and absorption were 0.990, 0.991, 0.998, 0.928, respectively. According to variance analysis of the data, there were significant differences between the effects of three variables (pH, temperature and time) on yield of extraction and viscosity, but no significant difference was observed between the effects of temperature and pH on gel strength and absorption, respectively. Comparisons of the averages of functional characteristics of acidic and commercial gelatin showed that viscosity and strength of acidic gelatin were higher than those of commercial one. The optimum conditions were found to be: pH=1.88, temp. 80°C and 118 min., to reach the highest yield and pH=1.88, temp. 60°C and 48 min. to get maximum strength, and pH=2.56, temp. 69°C and 118 min. to obtain the maximum viscosity and finally, pH=2.6, temp. 62°C and 48 min. for minimum absorption. Also, the results revealed that there were significant differences between trace elements content (Fe, Ca and Pb) of commercial and acidic gelatins. Although, acidic gelatin contained higher amount of the elements, but these amounts were still less than maximum values which are allowed to exist in gelatin. Amino acid compositions of both gelatins were almost identical.
M. Sabokdast , F. Khyalparast,
Volume 11, Issue 42 (1-2008)
Abstract
This research was conducted in order to determine the relationship between grain yield and yield components, using 30 common bean varieties in a randomized complete block design with four replications at the Agricultural filed faculty of Agriculture,Tehran university In this study 18 traits were assessed on 10 random plants from each plot. The result showed that there were significant differences among varieties in terms of trait under study, indicating the existence of genetic variation among varieties. Also results showed that the grain yield had a positive and significant genotypic correlation with number of seed/pod, pod weight, number of pod/plant, biological yield, days to flowering and maturity. Stepwise regression analysis showed that the maximum variation in grain yield could be attributed to the number pod/plant, number seed/plant, 100 seed weight and pod length. The results of path analysis showed that the highest direct effect, being positive, was related to number seed/plant and the lowest direct effect, which was related to number pod/plant. Factor analysis resulted in three factors that accounted for 78/7% of total variation. The first factor accounted for 38.39% of total variation and was designated as yield and yield component factor. This factor is comprised of pod weight, biological yield, grain yield and number of pod/plant traits.
N. Yaghmaeian Mahabadi, J. Givi,
Volume 11, Issue 42 (1-2008)
Abstract
Gypsum affects many physical, chemical and mineralogical properties which in turn influences management, classification and sutability of the soils. This is the reason why accurate measurement of gypsum in soil is very important. In most of the soil science laboratories, the method of acetone ,in spite of its too much limitation, is being used as a standard method. The purpose of this research was to compare different gypsum determination methods and to find the most suitable one. The study areas include Jafarabad of Borkhar and Sepahanshahr.Soil samples were collected from different horizons of the studied profiles and seven samples with a wide range of gypsum content were selected. Gypsum content of the soil samples were determined by methods of acetone, sodium carbonate, resin, calcium and magnesium difference, diluted extracted sulfate, ammonium carbonate, sodium citrate and hydrochloric acid. To calculate the recovery percentage of the methods, after adding a certain amount of gypsum with known purity percentage to the soil samples, gypsum content was determined again by above mentioned eight methods. To evaluate the suitability of the methods, in addition to the recovery percentage of the methods, coefficient of variability and extent of proximity of the regression line to the 1:1 line were used. The results revealed that among the used methods, the method of sodium carbonate is the most accurate one. Resin method is ranked as the second best method and can be used in non-saline soils as another accurate method for determination of gypsum content. Sodium citrate and hydrochloric acid methods for different amounts of gypsum and ammonium carbonate method for gypsum content up to 30% are third in rank as far as their accuracy is concerned. Acetone, calcium magnesium difference and diluted extracted sulfate methods are not sufficiently accurate, because of low solubility of gypsum in water which is used as an extractant. In general, the most important determinant of accuracy of the methods is extractants of the gypsum among which the sodium carbonate has the highest efficiency.
H. Jalilvand,
Volume 11, Issue 42 (1-2008)
Abstract
This study was down in Forest Park of Noor. In order to determination of tree ring response to climatic variations, 35 cores were taken from dominant natural stand of common ash (Fraxinus excelsior L.). The guide of this study was finding which climatic variables are effective in the ring width growth of ash in current growing year and previous years (one, two and three years before current growing year) by multiple regression models at the North of IR-Iran. Totally, 85 annually, monthly seasons and seasonal growth climatic variations of precipitation, temperature, heat index, evapotranspiration and water balance were analyzed. The best multiple regression models were explained 83 percent of total variance of the growth of common ash. The results show that the growth of common ash was related to the previous year's climatic variations than that of the current year. The most effective role of climatic variations was due to the first and second preceding years (55%). Evapotranspiration of July and September, and precipitation of May in the second and precipitation of March in the third previous years, all were positively affected the growth of this species. This study revealed that ash is interested in warmer condition on early and middle of seasonal growth in present of available humid, and precipitation in the months of early growing season (Ordibehesht-Khordad of two previous years).
H. Farhangfar, H. Naeemipour , R. Lotfi,
Volume 12, Issue 43 (4-2008)
Abstract
This study was undertaken to estimate genetic trend and parameters of Holstein cattle in Khorasan province for milk yield using a spline random regression test day animal model. A total of 32854 monthly test day milk records (twice and thrice a day milking) obtained from 3842 Holstein heifers (progeny of 466 sires) distributed in 125 herds and calved from 2001 to 2005 was used to predict breeding value of individual animals. In the model, fixed effects of herd including year-month of recording, milking times, age at calving (linear and quadratic covariables), Holstein gene percentage (linear covariable) as well as random effects of additive genetic and permanent environment were studied. To take account of the shape of the lactation curve at genetic and environmental levels, cubic spline polynomials were also included in the test day model. Bayesian method by applying Gibbs sampling technique (100000 chains applying RRGIBBS software) was utilized to obtain posterior means of predicted breeding value of animals for milk yield at individual month of lactation. The results showed that mean of breeding value for 305-day milk yield was 52.90 kg (p<0.05). Spearman rank correlations between predicted breeding values at different months of lactation decreased as the interval between them increased. The highest and lowest rank correlations were found between months 8 and 9 (0.998) and between months 1 and 10 (0.312), respectively. Predicted breeding value of 305-day milk had the lowest and highest rank correlations with predicted breeding value at months 1 (0.553) and 6 (0.990), respectively. Regression analysis of average predicted breeding value of progenies in their birth year showed that the amount of genetic trend for 305 day milk yield was 17.75 kg per year, statistically no different from zero (p value=0.165).
H. Yosef-Zadeh, M. Tabari, K. Spahbodi, Gh. Jalali,
Volume 12, Issue 44 (7-2008)
Abstract
In order to predict Caucasian maple (Acer velutinum Boiss. ) seedling growth based on nursery Orimel, Eighty six one year old seedlings located at 1550 meters above sea level in Sari, north of Iran were randomly selected. Collar diameter, height, leaf area, photosynthesis area and leaf area/leaf weight ratio were determined. Then multivariate regression models between leaf characteristics and growth characteristic were drawn. The results indicated that number of leaves and photosynthesis area can estimate the height growth of a seedling. Also, mentioned characteristics of leaf can estimate the biomass of stem as a well as growth characteristics. According to the correlation between growth characteristics and leaf characteristics, it would be concluded that the photosynthesis area of leaf can be suitable for early selection of seedling for reforestation. Also, this result shows the importance of increasing the establishment and growth of maple seedlings in plantation areas.
J. Abdollahi, N. Baghestani, M.h. Saveqebi, M.h. Rahimian,
Volume 12, Issue 44 (7-2008)
Abstract
The present study discusses a method used to produce updated information about vegetation cover in arid and semi-arid zones, using RS data and GIS technique. In this method, Landsat ETM+ data in 2002 was collected in an area of about 60000 ha in Nodoushan basin, Yazd, Iran. To collect the necessary ground data, 50 sites of different vegetation types were selected and the percentage of vegetation cover in each one was determined. Also, different vegetation and soil indices were derived and crossed with located sampling points using ILWIS software capabilities. To get the best fitted curve, the relationship between vegetation cover, as a dependent variable, and satellite data bands, vegetation indices and environmental factors, as independent variables were assessed. Therefore, a multiple linear regression model was established for the prediction of vegetation cover percentage in the studied area. Finally, a vegetation cover map with high a precision was produced. As a conclusion, it can be said that mapping of vegetation cover via remote sensing is possible even if its vegetation cover is sparse.
M Noruzi, A Jalalian, Sh Ayoubi, H Khademi,
Volume 12, Issue 46 (1-2009)
Abstract
Crop yield, soil properties and erosion are strongly affected by terrain parameters. Therefore, knowledge about the effects of terrain parameters on strategic crops such as wheat production will help us with sustainable management of landscape. This study was conducted in 900ha, of Ardal district, Charmahal and Bakhtiari Province to develop regression models on wheat yield components vs. terrain parameters. Wheat yield and its components were measured in 100 points. Points were distributed randomly in stratified geomorphic surfaces. Yield components were measured by harvesting of 1 m2 plots. Terrain parameters were calculated by a 3×3 m spacing from digital elevation model. The result of descriptive statistics showed that all variables followed a normal distribution. The highest and lowest coefficient of variance (CV) was related to grain yield (0.36) and thousand seeds weight (0.13), respectively. Multiple regression models were established between yield components and terrain parameters attributes. The predictive models were validated using validation data set (20% of all data). The regression analysis revealed that wetness index and curvature were the most important attributes which explained about 45-78% of total yield components variability within the study area. The overall results indicated that topographic attributes may control a significant variability of rain-fed wheat yield. The result of validation analysis confirmed the above-stated conclusion with low RMSE and ME measures.
A Amini, M Shahsavan, A Zeinal Hamedani,
Volume 12, Issue 46 (1-2009)
Abstract
Women as extension help-agents could play an important role in rural extension programs. This study was aimed at evaluating the success of women as extension help-agents, and factors affecting their success in Isfahan province, Iran. The data was randomly collected from 156 extension help-agents, using Cochran formula. The validity and reliability of constructed questioners were checked, using Cronbach Alfa and K.M.O. criteria. The results showed that 6.5 percent of the agents gained a success score of more than or equal to the average score, 50.3 percent equal to the average score, and 43.2 percent gained less than the average success score. The Effective factors are categorized as the degree of their familiarity with the problems of the population, the degree of their involvement in extension-educational programs, and factors such as their access to rural libraries, financial and occupational background and contribution to community and team work. According to the regression analysis results, participation activities of the villagers, financial status of the help-agents and educational programs provide most influential factors for successful extension programs.
M.m Majidi, A Mirlohi,
Volume 12, Issue 46 (1-2009)
Abstract
This experiment was conducted to investigate the genetic diversity, identify traits explaining yield variation, recognize relationships between traits and classify accessions in a Iranian and forign germplasem of tall fescue. Forty six Iranian and foreign tall fescue accessions were surveyed for Phenological, morphological and agronomical characters in a randomized complete block design with three replications in field for 2 years. Significant differences were observed for all of the characters, indicating broad variation in this germplasm. Iranian accessions had a better performance for most of the traits in both years indicating their high potential for developing commercial varieties in breeding programs. Basis on stepwise regression analysis, crown width justified the majority of hay yield variation, followed by establishment rate, percentage of dry matter, height and number of stem. Hence, these characters could be used for selecting high yielding cultivars. Factor analysis revealed 4 factors which explained more than 80 percent of the total variation and confirmed the results of regression analysis. Using UPGMA method, cluster analysis revealed five groups. Accessions with similar country of origin or same ecological conditions were grouped in same cluster. Regarding the morphological characters the best accessions were identified to be used in the further breeding projects.
