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--- documents:111012rtricks [2012/02/14 21:32] – added image plot kota
+++ documents:111012rtricks [2020/11/26 07:08] (current) – kota
@@ Line 4: / Line 4: @@
 When you import data from the out put of other software, you might have trailing 0s at the end of each column:
-<code>
+<code:R>
 > d0
  [1] 69.444 70.889 86.667 95.667 83.444 78.333 67.889
@@ Line 18: / Line 18: @@
 </code>
 To remove them, there could be many ways, but here is my one liner.
-<code R>
+<code:R>
 d0c <- d0[rev(cumsum(rev(d0)))>0]
 </code>
@@ Line 34: / Line 34: @@
 ===== Plotting a matrix data as a color-coded image =====
-<sxh>
+<code:R>
 #a 2Dplot, color coded.
+x <- c(1:20)
-for(j in seq(0, 9)){
+y <- c(1:10)
-  for(i in seq(0, 19)){
+for(j in y){
+  for(i in x){
     val <- i+j
-    if((i == 0) & (j == 0)) {
+    if((i == 0) & (j == 0)) z <- val
-      z <- val
+    elsez <- append(z, val)
-    } else {
-      z <- append(z, val)
-    }
   }
 }
-x <- c(1:20)
-y <- c(1:10)
 z <- matrix(z, nrow=20, ncol=10)
 mat <- list(x, y, z)
 image(x, y, z)
-</sxh>
+</code>
 [{{:documents:rtips:imageplot.png| Example plotting of a matrix using base graphics function image()}}]
+... a bit faster way calculation wise uses indexing.
+<code:R>
+width <- 10
+height <- 20
+x <- c(1:width)
+y <- c(1:height)
+xindex <-rep(x, length = width*height)
+yindex <- yindexing(x, y)
+z <- xindex + yindex
+z <- matrix(z, nrow=width, ncol=height)
+mat <- list(x, y, z)
+image(x, y, z)
+yindexing <- function (x, y) {
+  for(i in y){
+    cr <- rep(i, length=length(x))
+    if (i==1) all <- cr
+    else all <- append(all, cr)
+  }
+  return (all)
+}
+</code>
+===== Inserting math formula & symbols in label or title =====
+The easiest way is to use function //expression()//. For example,
+<code>
+plot(back$V2, type='l', xlab=expression(slice %.% time), ylab='intensity', xaxt="n", yaxt="n")
+</code>
+Inserts vertically centered dot in the x label between "slice" and "time". You could check other available expressions by
+<code>
+?plotmath
+</code>
+More recent, but under development is using [[http://cran.r-project.org/web/packages/tikzDevice/|tikzDevice]].
+===== Variable Name to String =====
+<code>
+myfunc <- function(v1) {
+  deparse(substitute(v1))
+}
+myfunc(foo)
+[1] "foo"
+</code>