[R] an apply question

[David Winsemius]

On Jan 18, 2013, at 9:17 PM, m p wrote:

> Hello,
> It should be easu but I cannot figure out how to use apply function.

Unless this is a homework question then using `apply` seems inefficient.
> I am
> trying to replace negative values in an array with these values + 24.
> Would appreciate help. Thanks,
> Mark
>
> shours <- apply(fhours, function(x){if (x < 0) x <- x+24})
> Error in match.fun(FUN) : argument "FUN" is missing, with no default

You should not use the assignment operator in the expression that  
forms the consequent for `ifelse`. (Furthermore apply takes three  
arguments and you only have two.)

Vectorize:

mat1<-matrix(sample(-10:10,40,replace=TRUE),ncol=5)

  mat1[mat1 < 0] <- mat1[mat1 < 0]+24
  mat1
      [,1] [,2] [,3] [,4] [,5]
[1,]    2    4   23    1    0
[2,]   18    7   10    3   16
[3,]   10   16   16   16    0
[4,]    3    3    6   17    3
[5,]   21    0    6    9   16
[6,]   10    4    6    0    0
[7,]    7    8   21    0   20
[8,]   19    7   15   19    5

>
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David Winsemius, MD
Alameda, CA, USA