On Jan 5, 2012, at 8:02 PM, Jonas Stein wrote:
> On 2012-01-05, Jonas Stein <n...@jonasstein.de> wrote:
>> i want to plot values with frequency on a logarithmic x axis.
>> similar to this example that i found in the web:
>> http://www.usspeaker.com/jensen%20p15n-graph.gif
>>
>> I would like to convert long numbers to si prefix notation
>> like in the example
>>
>> (200000 to 200k, 35000000 to 3.5 M)
>>
>> Of course i could create labels by hand, but
>> i have many files so i need some automatic function.
>>
>> Has anyone done that in R?
>>
>> Kind regards and thank you for your help,
>
> my first try looks like this:
> ==================================
>
> getSIstring <- function(x){
>
> sistring <- paste(x);
>
> prefixpairs <- data.frame(c(1e24,1e21,1e18,1e15,1e12,1e9,1e6,1e3,1e0,
> 1e-3,1e-6,1e-9,1e-12,1e-15,1e-18,1e-21,1e-24),
> c("Y", "Z", "E", "P", "T", "G", "M", "k", " ",
> "m", "u", "n", "p", "f", "a", "z", "y"))
>
> colnames(prefixpairs) <- c("factor", "prefix")
> i=0
> repeat{i=i+1;
> if (x > prefixpairs$factor[i]) {
> sistring <- paste(x/prefixpairs$factor[i], prefixpairs$prefix[i]);
> break;}
> if (i >= length(prefixpairs$factor)) break}
>
> return(sistring)
> }
>
> ==================================
>
>> getSIstring(2e7)
> [1] "20 M"
>
> How can i improve this function?
> It would be nice if it could handle lists too like sin() can do
>> sin(1:4)
> [1] 0.8414710 0.9092974 0.1411200 -0.7568025
>
How about using findInterval - that will give you the behavior you describe.
Note I had to reverse the order of your table and I did not make it a data
frame.
getSIstring <- function(x){
lut <- rev(c(1e24,1e21,1e18,1e15,1e12,1e9,1e6,1e3,1e0,
1e-3,1e-6,1e-9,1e-12,1e-15,1e-18,1e-21,1e-24))
pre <- rev(c("Y", "Z", "E", "P", "T", "G", "M", "k", " ",
"m", "u", "n", "p", "f", "a", "z", "y"))
ix <- findInterval(x, lut)
if (length(ix) > 0 ) {
sistring <- paste(x/lut[ix], pre[ix])
} else {
sistring <- as.character(x)
}
return(sistring)
}
> getSIstring(c(4.2e-3,2e7))
[1] "4.2 m" "20 M"
Cheers,
Ben
> kind regards,
>
> --
> Jonas Stein <n...@jonasstein.de>
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
Ben Tupper
Bigelow Laboratory for Ocean Sciences
180 McKown Point Rd. P.O. Box 475
West Boothbay Harbor, Maine 04575-0475
http://www.bigelow.org
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