[R] Reshape2, melt, order of categorical variable and ggplot2

[David Winsemius]

On Oct 7, 2012, at 1:40 PM, Stathis Kamperis wrote:

> Hello everyone,
> 
> I have the following data frame:
> 
>> df
>           V1     V2      V3
> 1   bench1_10  16675   16678
> 2   bench1_10  16585   16672
> 3  bench1_100 183924  185563
> 4  bench1_100 169310  184806
> 5  bench1_300 514430  516834
> 6  bench1_300 510743  514062
> 7  bench1_500 880146  877882
> 8  bench1_500 880146  857359
> 9   bench1_1k 880146 1589600
> 10  bench1_1k 880146 1709990
>> 
> 
> I'd like to melt it by using id=V1:
> 
>> mdf <- melt(df)
> Using V1 as id variables
>> mdf
>           V1 variable   value
> 1   bench1_10       V2   16675
> 2   bench1_10       V2   16585
> 3  bench1_100       V2  183924
> 4  bench1_100       V2  169310
> 5  bench1_300       V2  514430
> 6  bench1_300       V2  510743
> 7  bench1_500       V2  880146
> 8  bench1_500       V2  880146
> 9   bench1_1k       V2  880146
> 10  bench1_1k       V2  880146
> 11  bench1_10       V3   16678
> 12  bench1_10       V3   16672
> 13 bench1_100       V3  185563
> 14 bench1_100       V3  184806
> 15 bench1_300       V3  516834
> 16 bench1_300       V3  514062
> 17 bench1_500       V3  877882
> 18 bench1_500       V3  857359
> 19  bench1_1k       V3 1589600
> 20  bench1_1k       V3 1709990
>> 
> 
> My problem is that V1 in mdf has bench1_1k before bench1_500 and so
> on. This is a problem because when I try to plot the results with:
> 
> p <- ggplot(mdf, aes(x=mdf$V1, y=mdf$value))
> p <- p + geom_point(aes(colour=factor(mdf$variable)))
> p
> 
> I get bench1_1k in the horizontal axis before say bench1_500.
> 
> Is there any way to have V1 in mdf "sorted" just like in df ? Or do I
> have to rename my files from bench1_1k to bench1_1000 and be done ?

In all likelihood you need to review the care and feeding of the factor beasts under your care. The alpha ordering is the default and that will put "bench1_1k" in the middle. You canchange the levels however.

?levels

-- 

David Winsemius, MD
Alameda, CA, USA