[R] qqnorm & huge datasets

[cberry at tajo.ucsd.edu]

Sam Steingold <sds at gnu.org> writes:

> Hi,
> When qqnorm on a vector of length 10M+ I get a huge pdf file which
> cannot be loaded by acroread or evince.
> Any suggestions? (apart from sampling the data).
> Thanks.

Following the other suggestions, I did not notice mention of another
trick for slimming down graphs of many points. viz.

Do not plot points that substantially overlap:

> xx <- rexp(1e05)
> qq.results <- qqnorm(xx, plot.it=FALSE)
> qq.slim <- unique(round(as.data.frame(qq.results),3))
> dim(qq.slim)
[1] 10233     2
> plot(qq.slim)
> 

Choose the digits arg in round to be large enough to allow for points that do not overlap
to be seen and small enough to slim down the number of plotted
points. In the example above, 10233 vs 100000.

HTH,

Chuck

-- 
Charles C. Berry                            Dept of Family/Preventive Medicine
cberry at ucsd edu			    UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901