Hi,
On Nov 3, 2009, at 9:56 AM, Joel Fürstenberg-Hägg wrote:
Hi all,
I'm trying to write a script that changes all negative values in a
data frame column to a small positive value, based on the the
minimum value of the column.
However, I get the following error:
Error in if (x[i] < 0) { : argument is of length zero
This is telling you that x[i] is a zero length object, so you're
indexing is wrong
As well, I would "minimum" to be the smallest of the non-negative
values...
Aa_non_neg=(fieldTrial0809$Aa) # Copy column from data frame to
manipulate
nonNegative = function(x)
{
minimum=min(x) # Should only use positive minimum!
You have to tell R to only use positive numbers, min(x[x > 0]) would
have worked.
I'm not really sure what you're looping over below.
for (i in x)
{
if(x[i]<0) # Found a negative value
{
x[i]=minimum/10 # Change to a new non-negative value
}
}
}
This will work over each column of an "orig.df" data.frame (assumes
all cols are numeric) and generate the new data.frame you're looking
for:
new.df <- as.data.frame(apply(orig.df, 2, function(col) {
min.val <- min(col[col > 0])
col[col < 0] <- min.val
col
}))
-steve
--
Steve Lianoglou
Graduate Student: Computational Systems Biology
| Memorial Sloan-Kettering Cancer Center
| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact
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