Replacing several rows of a matrix at once
On 2010-11-28 19:53, Bryan Hanson wrote:
Hello Folks. This must be a silly question with a (not) obvious (to me) answer. Consider this: tmp<- matrix(1:200, nrow = 20) vec<- 300:309 tmp[9,]<- vec # replacing one row works fine p<- c(3, 11, 17) tmp[p,]<- vec # replacing multple rows pastes the values down a column and recycles vec. What I want to do is replace multiple rows simultaneously at once. I suppose I can write a function, but this seems pretty fundamental so I feel I must be missing some obvious alternative. I'm feeling like I'm in the Inferno!
Since matrices in R use column-major order, transpose first: ttmp <- t(tmp) ttmp[, p] <- vec (ans <- t(ttmp)) Peter Ehlers
TIA. Bryan ************* Bryan Hanson Professor of Chemistry& Biochemistry DePauw University, Greencastle IN USA
sessionInfo()
R version 2.12.0 (2010-10-15) Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit) locale: [1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8 attached base packages: [1] splines datasets tools grid grDevices graphics utils stats [9] methods base other attached packages: [1] survival_2.35-8 gridExtra_0.7 GGally_0.2.2 xtable_1.5-6 [5] mvbutils_2.5.1 ggplot2_0.8.8 proto_0.3-8 reshape_0.8.3 [9] ChemoSpec_1.46 seriation_1.0-2 colorspace_1.0-1 TSP_1.0-1 [13] R.utils_1.5.3 R.oo_1.7.4 R.methodsS3_1.2.1 rgl_0.92.794 [17] lattice_0.19-13 mvoutlier_1.4 plyr_1.2.1 RColorBrewer_1.0-2 [21] chemometrics_1.0 som_0.3-5 robustbase_0.5-0-1 rpart_3.1-46 [25] pls_2.1-0 pcaPP_1.8-3 mvtnorm_0.9-92 nnet_7.3-1 [29] mclust_3.4.6 MASS_7.3-8 lars_0.9-7 gclus_1.3 [33] cluster_1.13.1 e1071_1.5-24 class_7.3-2
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