[R] Using column length in plot gives error

[Stephanie Kovalchik]

Is spectra.wavelength a factor? If so, plot will treat it as  
categorical and not draw a line. Try the following modification.

plot(as.numeric(spectra.wavelength), cormat, type = "l", ylim=c(-1,1),  
xlab="Wavelength (nm)", ylab="Correlation")

Quoting MikSmith <mike at hsm.org.uk>:

>
> Hi
>
> I'm trying to write a generic script for processing some data which finishes
> off with some plots. Given Im never sure how many columns will be in my
> dataframe I wanted to using the following
>
> plot(spectra.wavelength, cormat, type = "l", ylim=c(-1,1), xlab="Wavelength
> (nm)", ylab="Correlation")
>
> however even if I specify as type="l" it appears plot as points (right hand
> plot). If I specify a range such as
>
> plot(650:700, cormat, type = "l", ylim=c(-1,1), xlab="Wavelength (nm)",
> ylab="Correlation")
>
> it looks good (left hand plot). If I try something like:
>
> plot(spectra.wavelength[1]:spectra.wavelength[length(spectra.wavelength)],
> cormat, type = "l", ylim=c(-1,1), xlab="Wavelength (nm)",
> ylab="Correlation")
>
> it fails with "variable lengths differ" and when I look at
> spectra.wavelength[1] it gives me the value but then states there are 53
> levels.
>
> What does this mean and how can I get the result I want??!
>
> many thanks
>
> mike http://www.nabble.com/file/p23562717/1.pdf 1.pdf
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