Dear R-helpers,
I have a huge data-set so need to avoid for loops as much as possible. Can
someone think how I can compute the result in the following example (that uses
a for-loop) using some version of apply instead (or any other similarly
super-efficient function)?
example:
#Suppose a matrix:
m1=cbind(1:5,1:5,1:5)
#The aim is to create a new matrix with every column containing the cumulative
sum of all previous columns.
m2=m1
for(i in 2:ncol(m1)){
m2[,i]=apply(m1[,1:i],1,sum)
}
m2
Many thanks in advance
Eleni Rapsomaniki
Research Associate
Strangeways Research Laboratory
Department of Public Health and Primary Care
University of Cambridge
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