[R] Bin Category Labels on Axis

[David Winsemius]

On Jun 16, 2009, at 6:13 PM, jproville wrote:

>
> Thanks David! I had trouble understanding how to convert factors,  
> and was
> playing around with as.numeric but it had never occurred to me to  
> use a
> combination of both that and as.character.

There's a FAQ on the topic.

> I am getting really close to the graph I want - I've played around  
> with the
> arguments however I am still hitting a snag, if you have any insight  
> as to
> how to solve this I would be really grateful:
>
> There seems to be some sort of difficulty in labeling axes spanning  
> from a
> negative integer to a positive - I am getting the following error  
> message
> Error in `[.default`(z$bins, seq(-36, 33, by = 5)) :
>  only 0's may be mixed with negative subscripts

Yeah, that's what you get for not including a test dataset ...  
untested code with bugs.

The second seq() for the labels argument should start with 1 and go to  
36 + 33 + 1. With your data you might first check to see if these  
register properly. What does this display

c( seq(-36, 33, by = 5), (z$bins[seq(1, 70, by = 5)] )


>
> Thanks again for your help!
>
> Jeremy Proville
> M.Sc. Candidate
> Bioresource Engineering, McGill University
>
>
>
>
> David Winsemius wrote:
>>
>> The canonical method of creating a numeric value from a factor is to
>> wrap the factor in as.numeric(as.character( (.))  The as.character
>> grabs the value from the factor levels rahter than giving you the
>> internal codings and the as.numeic finishes the job.
>>
>> Set xaxt=FALSE in the plot arguments. The axis can be managed with  
>> the
>> axis() function with at= and labels= arguments. You might want to not
>> plot every one of them, perhaps:
>>
>>  at = seq(-36, 33, by = 5) , labels = as.numeric(as.factor(z
>> $bins[seq(-36, 33, by = 5)] )),
>> -- 
>> David Winsemius
>>
>> On Jun 15, 2009, at 7:09 PM, jproville wrote:
>>
>>>
>>> Hi,
>>>
>>> I'd really appreciate if someone could give me some help or advice
>>> about
>>> this - I've tried everything I know and am clueless about how to
>>> proceed!
>>>
>>> I've written a script to import ASCII data of raster maps, bin them
>>> into
>>> categories, calculate the mean values within these bins and plot the
>>> two in
>>> a simple graph. I'm running into problems with my x axis, as R
>>> cannot add
>>> the bin categories as labels and simply outputs the factor values of
>>> the
>>> number of bins.
>>>
>>> In much more detail:
>>> One set of data is fractional values for the amount of cropland in a
>>> designated area (raster cell). The second is annual average
>>> temperature
>>> data, in the same format. I import these using:
>>> xRaw<-scan(".../Temp.txt")
>>> yRaw<-scan(".../Cropland.txt")
>>>
>>> and then designate cells with values of -9999 as NAs:
>>> x<-ifelse(xRaw==-9999,NA,xRaw)
>>> y<-ifelse(yRaw==-9999,NA,yRaw)
>>>
>>> Then, I compile them into a 2 column data frame, and exclude the NA
>>> values:
>>> zRaw<-data.frame(x,y)
>>> z<-na.exclude(zRaw)
>>>
>>> I am then left with data frame 'z' which is a refined list of data.
>>> Using
>>> the 'cut' function, I assign each row into one of 69 different bins:
>>> z$bins<-cut(z$x, breaks=c(-36:33), include.lowest=TRUE)
>>>
>>> Each bin is now 1 degree Celsius wide. Within each one, I calculate
>>> the mean
>>> value of the corresponding fractional cropland data:
>>> a<-tapply(z$y, z$bins, mean)
>>>
>>> Object 'a' now contains each bin category and the associated mean
>>> cropland
>>> values, so 69 points in total.
>>>
>>>
>>> Now, a problem arises when I try and plot these values using:
>>> plot(a, xlab="Temperature", ylab="Fraction of Cropland", pch=20)
>>> What happens is that R intuitively labels my x-axis from 1-70, which
>>> corresponds to the bin factor values that were returned when the  
>>> 'cut'
>>> function was used. I would like to simply label the x-axis with my
>>> temperature values, from -36 degrees to 33 degrees, instead of  
>>> having
>>> numbers 1-69. How can I do this??
>>>
>>> Thanks,
>>>
>>> Jeremy Proville
>>> M.Sc. Candidate
>>> Bioresource Engineering, McGill University
>>> -- 
>>> View this message in context:
>>> http://www.nabble.com/Bin-Category-Labels-on-Axis-tp24042325p24042325.html
>>> Sent from the R help mailing list archive at Nabble.com.
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> David Winsemius, MD
>> Heritage Laboratories
>> West Hartford, CT
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
> -- 
> View this message in context: http://www.nabble.com/Bin-Category-Labels-on-Axis-tp24042325p24063836.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT