• []: subscript a string
• as.matrix.data.frame(data): convert data to a matrix
• image.plot(x, y, matrix): color matrix (library(filds))
• attach, detach: open/close table
• read.table(…):
  • skip=n: begin to read rows after n rows
  • row.names=n: the row names are in column n
  • fill=TRUE: show missing values
  • na.strings=“N.A.”“: transform N.A. in NA (missing values)
• for(i in 1:ncol(data)) if(is.numeric(data[,i])) data[is.na(data[,i]),i] ← 0: transform all NA to 0
• object ← cbind(object, as.matrix(“newColumn”)): add new column or row(rbind) to an existing matrix
• byrow=TRUE (in matrix): makes the matrix row by row (instead of column by column)
• legend.lab: write a legend in image.plot
• dimnames(matrix) ← list(row names, col names): name rows and columns in a matrix
• las: rotation of text margins

legend.args=list( text=“Number of different Allels (FST)”, cex=1.0, side=4, line=2)