In R how would you replace values in a matrix that have a certain condition with values from another vector?

user_17974332 0
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I have a matrix and a vector like this:

Matrix<-cbind(c(3,3,5,1),c(2,5,2,1))
Vector<-c(2,3,3,3)

I want to replace the Matrix elements that are >= the corresponding Vector value with the values in the Vector so that the Matrix would now look like this:

MatrixNew<-cbind(c(2,3,3,1),c(2,3,2,1))

What logic would achieve this?

vector r matrix
3 Answers

Thought you had to use apply(Matrix, \(x) pmin(x, Vector)), but actually, you can just use pmin() directly on your Matrix because it will recycle the Vector to match the length.

pmin(Matrix, Vector)
#>      [,1] [,2]
#> [1,]    2    2
#> [2,]    3    3
#> [3,]    3    2
#> [4,]    1    1
user_103573830

I believe the pmin method by @caldwellst is the simplest one so far. Here is another option using ifelse

> ifelse(Matrix >= Vector, Vector, Matrix)
     [,1] [,2]
[1,]    2    2
[2,]    3    3
[3,]    3    2
[4,]    1    1
user_121587570

It is also possible to do it with dplyr::mutate. It is interesting when you have to select a subset of variables.

library(dplyr)        
dd = structure(list(V1 = c(3, 3, 5, 1), ` V2` = c(2, 5, 2, 1), Condition = c(2, 
                3, 3, 3)), class = "data.frame", row.names = c(NA, -4L))
dd %>% mutate(across(contains('V'), ~ifelse(.>=Condition, Condition,. )))
      V1  V2 Condition
    # 1  2   2         2
    # 2  3   3         3
    # 3  3   2         3
    # 4  1   1         3
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