Hello, I’m new at programming and I will greatly appreciate if you can help me
with this.
I have a very large matrix (hundreds of rows and columns), with the first raw
filled with different numbers (between 0 and 1). The rest of the matrix is
filled with values 0, 1, 2. What I need is to replace the values in the matrix
(except the first row will has to remain intact). In each column I have to
replace value 2 for the value of the first row. Also, I want to replace the
values 0 and 1 by -999. I was able to write the loop for a vector but I do not
know how to expand the loop to the matrix.
Please see these examples
For a vector I did this and it works
> V = c(0.1,1,0,2)
> V
[1] 0.1 1.0 0.0 2.0
> for (i in 2:length(V)){if(V[i]==2)V[i]=V[1]
+ else (V[i]=-999)}
> V
[1] 0.1 -999.0 -999.0 0.1
For a matrix I could not perform the task. Here it is an example of a small
matrix and the expected result, but the original has more rows and columns.
> matr <- matrix(c(0.1,1,0,2,0.5,1,2,2), nrow=4, ncol=2)
> matr
[,1] [,2]
[1,] 0.1 0.5
[2,] 1.0 1.0
[3,] 0.0 2.0
[4,] 2.0 2.0
> matr.expectedresult= matrix(c(0.1,-999,-999,0.1,0.5,-999,0.5,0.5), nrow=4,
> ncol=2)
> matr.expectedresult
[,1] [,2]
[1,] 0.1 0.5
[2,] -999.0 -999.0
[3,] -999.0 0.5
[4,] 0.1 0.5
Thank you very much
Paula
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