R help - Sep 2008 - Plotting using 'if' statements

Dear all,

I have a dataset of four columns, and I wish to plot (as a scatter graph) the
values of the third column where the values are greater than zero, and the
fourth column.

I tried doing this via the plot command itself, but got into a bit of a mess
(resulting in errors!). My dataframe is called 'January':
> plot(January[3(>0):4])
Error: unexpected '>' in "plot(January[3(>"


After a few variations on this, I thought I'd try making a new object which
includes all values from the third column of January>0 (to plot in a separate
step) as follows:
> JanFilter <- January[3]>0
No error here. However, when I display the 'values' of JanFilter, it
shows that instead of keeping the numerical values, the above operation simply
displays the results of the logical test:
> head(JanFilter)
                             Value
[1,]                       FALSE
[2,]                        TRUE
[3,]                        TRUE
[4,]                        TRUE
[5,]                        TRUE
[6,]                        TRUE


This is obviously no good for plotting the numerical values on axes!

So my question is, how do I perform 'if' statements in order to filter
out various parts of a dataset, for plotting on a graph.

Many thanks,

Steve

Try this:

plot(January[January[,3] > 0, 3:4])

On Thu, Sep 4, 2008 at 1:28 PM, Steve Murray <smurray444@hotmail.com>
wrote:
>
>
> Dear all,
>
> I have a dataset of four columns, and I wish to plot (as a scatter graph)
> the values of the third column where the values are greater than zero, and
> the fourth column.
>
> I tried doing this via the plot command itself, but got into a bit of a
> mess (resulting in errors!). My dataframe is called 'January':
>
> > plot(January[3(>0):4])
> Error: unexpected '>' in "plot(January[3(>"
>
>
> After a few variations on this, I thought I'd try making a new object
which
> includes all values from the third column of January>0 (to plot in a
> separate step) as follows:
>
> > JanFilter <- January[3]>0
>
> No error here. However, when I display the 'values' of JanFilter,
it shows
> that instead of keeping the numerical values, the above operation simply
> displays the results of the logical test:
>
> > head(JanFilter)
>                             Value
> [1,]                       FALSE
> [2,]                        TRUE
> [3,]                        TRUE
> [4,]                        TRUE
> [5,]                        TRUE
> [6,]                        TRUE
>
>
> This is obviously no good for plotting the numerical values on axes!
>
> So my question is, how do I perform 'if' statements in order to
filter out
> various parts of a dataset, for plotting on a graph.
>
> Many thanks,
>
> Steve
>
> ______________________________________________
> R-help@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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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