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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and provide commented, minimal, self-contained, reproducible code.
