In R, square brackets [] are called "extraction operators" as they are interpreted so as to "extract" the parts of an object specified by the information within them. Your message contained only part of the line below:
AltB<-svdatstr[row,indicesA][svdatstr[row,indicesA]<svdatstr[row,"maxB"]] Extraction operators may be specified sequentially or nested. Both are used in this line. However, to understand how it works, first look at the line that defines the value of "indicesA": indicesA<-count_ind[as.logical(match(svdatstr[row,type_ind],"A",0))] This defines a vector of logical (TRUE/FALSE) values for the valid "Count" values in the current row by finding the matches in the "type" values for the character string "A". The reason I have used the "match" function instead of "=="" is to get rid of the NA values that would have been generated by specifying "0" (zero) in the "incomparables" argument. I then used the "as.logical" function to transform the "1" AND "0" to TRUE and FALSE..This logical vector can then be placed within square brackets to "extract" the valid "Count" values that have a "type" of "A" in the current row of svdatstr. Having done this, the expression within the latter pair of extraction operators can be translated as "Return a logical vector in which the TRUE values correspond to the "Count" values with a type of "A" that are less than the maximum value for type "B" count values". The expression within the first pair of extraction operators can be translated, "Extract all of the values of "Count" with a type of "A" in the current row". So, the second extraction then operates on those values, producing a vector of all of the "Count" values that are less than the value of "maxB". The line following this in the code uses the same logic to extract those values that are greater than or equal to "maxB". Jim On Thu, Apr 21, 2016 at 11:25 PM, sri vathsan <srivib...@gmail.com> wrote: > Dear Jim, > > I hope, I am not pestering you. When I was studying your code to grasp and > learn and found one thing which I can not understand the following line. I > would be grateful If you could tell what it exactly denote and this helps me > to grow better in R. > > I understand the first part of the code will check the rows of indicesA, but > I finding difficulty to grasp the second part starting with the square > bracket. > > "AltB<-svdatstr[row,indicesA][svdatstr[row,indicesA]" > ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
