[R] reference text variables as column name to plot

[David Winsemius]

On Nov 30, 2010, at 11:40 AM, Graves, Gregory wrote:

> Having given myself carpal tunnel looking for answer to this ...
>
>
>
> I have a dataset

Named.... what?

> each column of which has 12 rows in it.  I created a
> variable 'z' as follows:
>
>
>
> z=1:24  s


Why did you put twice as many elements in z as there are in a column?

>
>
>
> Since I have a large number of these plots to make, and they are a bit
> complex, I want to want to reference the column I want to plot via a
> variable containing the name of that column.  As follows:
>
>
>
> similar='1978'
>
> s=paste('Y',similar,sep='')
>
>
>
> variable s now contains 'Y1978' which is the name of one of the  
> columns.
>
>
>
> However, when I try to plot
>
>
>
> plot(z,s,type='l')

Try this ... assuming that there really are 12 item length columns in  
a dataframe named, dfm.

plot(1:12, dfm[[s]], type="l")

dataframes are lists that can be accessed by the names of columns  
which are interpreted. Don't assume that you can get such  
interpretation with the $ operator.
>
>
>
> I get a 'x and y lengths differ' error because variable s is being
> recognized as 'Y1978' length=1, rather than the contents of the column
> Y1978 length=12.
>
> I tried all the usual tricks I know like &s.

Huh? "&" is a logical operator.

>  How do you get R to
> reference a variable as a column name?
>
>
>
> Thank you.
>
>
>
> Gregory A. Graves, Lead Scientist
>
> Everglades REstoration COoordination and VERification (RECOVER)
>
> Restoration Sciences Department
>
> South Florida Water Management District
>
> Phones:  DESK: 561 / 682 - 2429
>
>                   CELL:  561 / 719 - 8157
>
>
>
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT