[R] a pickle with ranks and reals?
John Christie
jc at or.psychology.dal.ca
Fri Aug 22 06:44:06 CEST 2003
I predicted that y would increase as x increased. However, I only made
the prediction on the ranks of the scores. The ranks don't correlate
with predicted. And, I don't think a regression on the ranks is
warranted. However, the actual scores do yield a significant slope for
b, and a significant R^2 using a linear regression (y is the value and
x is the predicted rank). What should my argument be here? Should I
have endorsed using the actual scores instead of ranks to begin for
some reason that doesn't have anything to do with my current result? :)
Oh, on another note, I can use rcorr to get the Spearman correlations,
but I'd like to be able to just add
the ranks as a column. I was going to just use order and add a simple
factor. But, that doesn't deal with ties correctly.
And, I also wanted to analyze correlations subject by subject and
compare my two groups. However, there doesn't seem to be a good way to
get this. I tried using "by" with "cor". However, this requires
binding x and y which causes cor to return a matrix (if you could pass
it x and y separate it would just return a number).
given
data frame s
x y subj
4 7 harry
5 1 harry
6 9 harry
2 4 steve
3 7 steve
...
i'd like to be able to produce
r subj
.12 harry
.52 steve
...
any tips?
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