[R] If Statement

[David Winsemius]

On Mar 8, 2011, at 7:07 AM, dpender wrote:

> Hi,
>
> I am having some problems using the if statement correctly.  I have  
> used it
> many times previously so I dona't know what is different with this  
> case.
> Here is my problem:
>
> I have a 1X10 matrix of values as follows:
>
>> H.MC
>          [,1]
> [1,] 4.257669
> [2,] 7.023242
> [3,] 4.949857
> [4,] 5.107000
> [5,] 4.257669
> [6,] 4.257669
> [7,] 4.257669
> [8,] 4.257669
> [9,] 4.257669
> [10,] 4.257669
>
> What I want to do is replace all the values if 4.257669 with a  
> random number
> between 3 and 4.5.  To do this I have:
>
> H.MC.fin <- matrix(0,10,1)
>
> for (j in 1:10) {
>
> if(H.MC[j] == 4.257669)

Testing for equality of floating point numbers is a common source of  
errors. See the FAQ.

-- 
David.
> H.MC.fin[j] <-runif(1,3,4.5) else H.MC.fin[j] <-
> H.MC[j]
>
> }
>
> This doesn't seem to do anything and H.MC.fin is the same as H.MC.
>
> Does anyone know what I am doing wrong?
>
> Thanks,
>
> Doug
>
>
> --
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>
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David Winsemius, MD
West Hartford, CT