I think the 0 values for snail are hurting you. Kees
On Sunday 15 October 2006 13:10, zhijie zhang wrote: > Dear friends, > when i use glm() to fit my data, i use > glm(formula = snail ~ vegtype + mhveg + humidity + elevation + soiltem, > *family = Gamma(link = inverse),* data =a,)) > It shows: error in eval(expr, envir, enclos) : *gamma distribution don't > allow negative value*. > > But i use > result<-glm(formula = snail ~ vegtype + mhveg + humidity + elevation + > soiltem, family = poisson, data =a) #this works > In fact , there isn't any negative value in my dataset, who can tell me > the reason? > Thanks very much! > I copy my data here so you can check it: > vegtype mhveg humidity soiltem elevation snail > 1 diluo 35.0 0.279851 21.1 low 162 > 2 diluo 25.0 0.316092 23.1 low 113 > 3 yuhao 35.0 0.297238 21.7 low 105 > 4 huanghuacai 1.5 0.310687 23.1 low 5 > 5 huanghuacai 2.0 0.267868 28.3 low 1 > 6 yuhao 25.0 0.290135 21.9 low 10 > 7 huanghuacai 1.0 0.285207 27.7 low 6 > 8 huanghuacai 2.0 0.252973 28.3 low 1 > 9 huanghuacai 1.5 0.270000 28.1 low 1 > 10 huanghuacai 2.5 0.300000 29.1 low 1 > 11 huanghuacai 2.0 0.296154 29.1 low 0 > 12 huanghuacai 2.0 0.302874 27.5 low 3 > 13 huanghuacai 1.5 0.301499 28.9 low 0 > 14 huanghuacai 3.0 0.291513 30.3 low 1 > 15 huanghuacai 1.0 0.273438 31.1 low 3 > 16 huanghuacai 1.5 0.290116 27.9 low 19 > 17 huanghuacai 2.5 0.198932 31.9 low 0 > 18 huanghuacai 2.0 0.390000 30.5 high 4 > 19 huanghuacai 2.5 0.282595 30.7 high 0 > 20 huanghuacai 1.0 0.266097 24.7 high 14 > 21 yuhao 30.0 0.240516 26.9 high 51 > 22 yuhao 35.0 0.227541 26.7 high 84 > 23 yuhao 20.0 0.252833 28.3 low 30 > 24 diluo 40.0 0.303030 27.9 low 91 > 25 hucao 80.0 0.303867 24.5 low 114 > 26 diluo 25.0 0.334948 26.7 low 115 > 27 hucao 60.0 0.306897 26.5 low 23 > 28 hucao 75.0 0.314465 25.7 low 43 > 29 yuhao 30.0 0.251783 26.1 low 77 > 30 diluo 10.0 0.277778 26.1 low 62 > 31 yuhao 25.0 0.291716 26.1 low 78 > 32 hucao 90.0 0.288800 24.5 low 35 > 33 diluo 25.0 0.337830 26.3 high 75 > 34 yuhao 13.0 0.296599 27.7 high 23 > 35 hucao 70.0 0.279498 26.3 high 116 > 36 diluo 3.0 0.281481 28.1 high 25 > 37 hucao 70.0 0.296000 23.7 high 83 > 38 diluo 10.0 0.272662 27.7 low 56 > 39 hucao 70.0 0.289796 25.3 high 112 > 40 diluo 5.0 0.339716 27.9 high 84 > 41 yuhao 35.0 0.231427 24.9 high 88 > 42 hucao 80.0 0.273810 24.1 high 134 > 43 yuhao 40.0 0.272789 25.1 high 53 > 44 yuhao 45.0 0.226036 25.1 high 88 > 45 yuhao 55.0 0.285495 23.9 high 76 > 46 hucao 80.0 0.252185 23.9 high 106 > 47 diluo 15.0 0.289933 24.5 high 194 > 48 hucao 95.0 0.261756 23.1 high 35 > 49 hucao 55.0 0.239819 24.7 high 21 > 50 hucao 75.0 0.254307 23.9 high 41 > 51 huanghuacai 1.0 0.286432 23.7 low 18 > 52 huanghuacai 2.0 0.301342 23.1 low 2 > 53 huanghuacai 2.0 0.369565 23.3 low 5 > 54 huanghuacai 1.5 0.245833 24.3 low 4 > 55 huanghuacai 1.0 0.315679 24.1 low 4 > 56 huanghuacai 2.5 0.296124 23.7 low 4 > 57 huanghuacai 2.0 0.312667 25.7 low 3 > 58 huanghuacai 3.0 0.300870 25.7 low 0 > 59 huanghuacai 2.0 0.303743 26.5 low 2 > 60 huanghuacai 1.0 0.269799 25.3 low 7 > 61 hucao 75.0 0.281250 22.5 low 14 > 62 yuhao 35.0 0.350350 23.3 low 63 > 63 hucao 65.0 0.304545 22.7 low 17 > 64 diluo 7.0 0.310056 24.9 low 45 > 65 hucao 80.0 0.288000 22.9 low 27 > 66 hucao 80.0 0.284211 22.7 low 46 > 67 diluo 25.0 0.281379 23.5 low 161 > 68 hucao 80.0 0.290533 23.3 low 117 > 69 yuhao 27.0 0.316568 24.1 low 106 > 70 yuhao 28.0 0.285156 25.1 low 82 > 71 yuhao 30.0 0.266667 24.5 low 55 > 72 hucao 85.0 0.290345 23.9 low 54 > 73 yuhao 35.0 0.315789 24.1 low 81 > 74 diluo 15.0 0.286598 28.3 low 102 > 75 yuhao 45.0 0.314211 24.1 low 85 > 76 yuhao 25.0 0.268794 25.1 low 63 > 77 hucao 80.0 0.275691 23.9 low 59 > 78 hucao 100.0 0.316614 24.1 low 46 > 79 yuhao 40.0 0.336683 25.5 low 70 > 80 diluo 20.0 0.270874 26.1 high 167 > 81 yuhao 50.0 0.271483 24.3 high 125 > 82 hucao 80.0 0.238095 25.1 high 200 > 83 yuhao 30.0 0.241202 26.7 low 122 > 85 diluo 35.0 0.244531 28.1 high 186 > 86 yuhao 55.0 0.274038 24.9 low 208 > 87 hucao 80.0 0.303488 25.7 low 87 > 88 hucao 85.0 0.278846 25.3 low 25 > 89 diluo 5.0 0.270330 28.3 high 18 > 90 yuhao 35.0 0.296296 24.7 high 21 > 91 diluo 1.0 0.274306 27.9 low 23 > 92 diluo 3.0 0.262673 29.5 low 0 > 93 diluo 8.0 0.268750 27.7 high 21 > 94 hucao 70.0 0.265734 26.1 high 2 > 95 hucao 85.0 0.275373 24.3 low 6 > 96 diluo 10.0 0.284091 27.1 low 2 > 97 hucao 85.0 0.268229 25.3 low 0 > 98 hucao 90.0 0.293056 23.9 low 0 > 99 yuhao 35.0 0.277483 24.7 low 3 > 100 hucao 95.0 0.286822 24.3 high 1 > 101 hucao 88.0 0.285946 23.9 high 5 > 102 yuhao 35.0 0.268313 24.5 low 1 > 103 yuhao 25.0 0.285714 24.3 high 0 > 104 yuhao 25.0 0.294675 24.5 high 2 > 105 yuhao 38.0 0.275385 23.5 high 6 > 106 hucao 92.0 0.302415 23.3 low 15 > 107 hucao 83.0 0.276190 23.9 low 5 > 108 yuhao 55.0 0.285068 24.1 low 20 > 109 hucao 80.0 0.276552 23.5 low 5 > 110 hucao 95.0 0.281818 23.9 low 0 > 111 hucao 105.0 0.270293 23.1 low 13 > 112 hucao 95.0 0.291209 20.1 low 23 > 113 hucao 90.0 0.273196 20.9 low 48 > 114 yuhao 27.0 0.261986 20.5 low 49 > 115 yuhao 40.0 0.265187 20.5 low 9 > 116 yuhao 27.0 0.307143 20.9 low 27 > 117 yuhao 33.0 0.293194 20.7 low 34 > 118 yuhao 25.0 0.211399 20.9 low 38 > 119 yuhao 20.0 0.277372 21.7 low 30 > 120 hucao 95.0 0.346224 20.5 low 88 > 121 hucao 90.0 0.330380 21.3 low 91 > 122 yuhao 23.0 0.337884 23.3 low 70 > 123 hucao 80.0 0.322488 22.3 low 103 > 124 hucao 80.0 0.300000 22.1 low 51 > 125 hucao 100.0 0.326241 21.7 low 82 > 126 hucao 95.0 0.298571 21.9 low 104 > 127 hucao 95.0 0.296029 21.7 low 39 > 128 hucao 85.0 0.260082 21.7 low 73 > 129 hucao 93.0 0.304167 21.9 low 103 > 130 hucao 90.0 0.289941 22.3 low 65 > 131 hucao 85.0 0.339189 22.7 low 112 > 132 yuhao 30.0 0.314103 23.3 low 32 > 133 yuhao 28.0 0.293464 23.5 low 29 > 134 yuhao 45.0 0.310256 23.3 low 92 > 135 yuhao 42.0 0.375573 23.1 low 49 > 136 hucao 90.0 0.313846 23.1 low 47 > 137 yuhao 25.0 0.303601 23.9 low 54 > 138 hucao 85.0 0.339394 23.3 low 64 > 139 hucao 90.0 0.285934 23.1 low 68 > 140 yuhao 27.0 0.327915 23.9 low 62 > 141 hucao 85.0 0.372679 23.9 low 94 > 142 hucao 85.0 0.350147 22.5 low 174 > 143 yuhao 35.0 0.278014 23.7 low 38 > 144 hucao 100.0 0.327273 22.9 low 105 > 145 hucao 68.0 0.309286 24.9 low 105 > 146 hucao 85.0 0.279503 24.3 high 60 > 147 hucao 95.0 0.310870 23.3 high 42 > 148 hucao 95.0 0.309353 24.3 high 64 > 149 hucao 92.0 0.280745 23.5 low 37 > 150 yuhao 25.0 0.300355 24.3 high 107 > 151 yuhao 40.0 0.307692 24.7 high 86 > 152 hucao 40.0 0.273292 25.3 high 72 > 153 hucao 53.0 0.305096 24.7 high 109 > 154 hucao 50.0 0.306288 24.7 high 76 > 155 hucao 95.0 0.312268 22.3 low 60 > 156 hucao 90.0 0.301170 22.7 low 62 > 157 yuhao 38.0 0.305109 22.9 low 68 > 158 hucao 25.0 0.300719 25.3 low 21 > 159 hucao 80.0 0.252149 23.1 low 50 > 160 hucao 90.0 0.290306 23.3 low 63 > 161 hucao 33.0 0.293772 25.1 low 63 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide 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