On Aug 7, 4:02 pm, Brad <[email protected]> wrote:
> Hi,
>
> I just downloaded and installed v4.7 of Sage on Mac OS X 10.6.8.
>
> I really like the application and appreciate all of the hard work the
> Sage team has done to produce this great software package.

Great!

> Lately, I have been trying to learn R and rpy2 for statistical
> analyses.

Good.

> Unfortunately, I have been experiencing some problems as I work
> through the rpy2 documentation pages (http://rpy.sourceforge.net/rpy2/
> doc-2.0/html/introduction.html#getting-started) from within Sage.

Yes, there aren't that many people using rpy2 with Sage - for
instance, William Stein found something nasty about Numpy and rpy2 not
that long ago, at least them not working together in Sage:
http://flask.sagenb.org/home/pub/57/  (I assume this worksheet still
exists?)

>
> For instance, this simple worksheet input,
>
> ---------------------------------
> import rpy2.robjects as robjects
> piplus2 = robjects.r('pi') + 2
> ---------------------------------

sage: piplus2 = robjects.r('pi')+int(2)

should work.  The problem is that we don't have much casting to RPy;
most of the work has gone into the R pexpect interface instead,
working directly with R.  I find RPy confusing, myself :) and work
directly with R, though I do have to use r.eval("stuff") a lot for
positional arguments, which don't always work well with it.


> ---------------------------------
>
> I then switched to r mode on the worksheet and typed a set of R
> commands given in the same rpy2 documentation:
>
> ---------------------------------
> ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
> trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
> group <- gl(2, 10, 20, labels = c("Ctl","Trt"))
> weight <- c(ctl, trt)
> anova(lm.D9 <- lm(weight ~ group))
> summary(lm.D90 <- lm(weight ~ group - 1))# omitting intercept
> ---------------------------------

Hmm, that surprises me.  This should not be calling rpy2.

I get

Analysis of Variance Table

Response: weight
          Df Sum Sq Mean Sq F value Pr(>F)
group      1 0.6882 0.68820  1.4191  0.249
Residuals 18 8.7293 0.48496

Call:
lm(formula = weight ~ group - 1)

Residuals:
    Min      1Q  Median      3Q     Max
-1.0710 -0.4938  0.0685  0.2462  1.3690

Coefficients:
         Estimate Std. Error t value Pr(>|t|)
groupCtl   5.0320     0.2202   22.85 9.55e-15 ***
groupTrt   4.6610     0.2202   21.16 3.62e-14 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.6964 on 18 degrees of freedom
Multiple R-squared: 0.9818,     Adjusted R-squared: 0.9798
F-statistic: 485.1 on 2 and 18 DF,  p-value: < 2.2e-16


My guess is that you still had some residue of weirdness left over
from having imported rpy2.  Try restarting the worksheet and NOT
importing rpy2.

Good luck!  We really value contributions from R users.  By the way,
another open source project you may find interesting (though it
wouldn't integrate with Python/Sage) is http://rstudio.org/.

- kcrisman

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