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rthresholdcontinuous

Compare values with a given standard row by row and write just 1 number for each row (exceeds / doesn't exceed the standard)

I have a matrix with many rows. Let's say

M = matrix(1:20, nrow = 4, ncol = 5)

And I have a threshold variable, e.g.

threshold = c(4,7,11,14,17)

Now I want R to compare each row in the matrix with this threshold value by value and tell me whether at least one value in that row exceeds this threshold's corresponding value. I.e., M[1,1] should be compared with threshold [1], M[1,2] with threshold [2] etc.

Ideally I would like to have a new variable, let's call it check, with just 1/FALSE (there is at least 1 value in the row exceeding the threshold) or 0/TRUE (no such values). Till now, what I could program is this:

check = apply (M, MARGIN=1, (ifelse((M[,] < threshold), 1, 0)))

check = apply (check, MARGIN=1, sum)

check = check == 0

But there are 3 problems with it:

  1. Maybe it's not the best way to solve the problem? I have a lot of data, and I think it can work very slowly..

  2. It doesn't work, R says:

    check = apply (M, MARGIN=1, (ifelse((M[,] < threshold), 1, 0))) Error in match.fun(FUN) : '(ifelse((M[, ] < threshold), 1, 0))' is not a function, letter or symbol

  3. Even if I perform just

    ifelse((M < threshold), 1, 0)

for the first row I get 

[1,]    1    1    1    0    0

Which is not true, because there are no values in the first row that exceed the threshold. It seems that R just compares the whole first row with the 1st element of threshold, then the whole 2nd row with the second value etc., and that's not what I want...

Many thanks in advance!

Solution 
  • apply(M, 1, function(x) max(diag(sapply(x, function(y) y >threshold))))