[R] RE: [R] A couple of little R things I can't figure out (column percents, regression with lagged variables)

[stecalza@tiscali.it]

Try with prop.table(hmm,#)

put # = 1 for row percentages # = 2 for column ones

Stefano

-- Messaggio Originale --

>Simple usage questions that I ought to be able to figure on my own, but

>can't.
>
>1.I'm able to produce a cross tabulation table showing counts with 
>either table or xtabs.  But I want column percentages for 
>interpretation, and it seems stupid to sit there with a calculator 
>figuring marginals and column percentages.  How to make R do it after this:
>
> > x <- c(1,3,1,3,1,3,1,3,4,4)
> > y <- c(2,4,1,4,2,4,1,4,2,4)
> > hmm <- table(x,y)
> > hmm
>    y
>x   1 2 4
>   1 2 2 0
>   3 0 0 4
>   4 0 1 1
>
>#I can get the column sums:
> > tots <- apply(hmm,2,sum)
>
>and I can get the total N of counts, but don't understand how to make it
>
>calculate column percents, as in
>
>     y
>
>x   1    2     4
>   1 100 66.67  0
>   3  0   0     80
>   4  0   33.33 20
>
>Pointers appreciated.
>
>
>2. A student said here's  y, a vector representing a time series, and 
>here's x, a vector representing a time series. I want to do a 
>conventional regression of y on the lag of x. In sas you do xlag=lag(x)

>and then use xlag in a regresson.  I just want something simple like 
>lm(y~lag(x)). But in R base there's no lag.
>
>So I can get it the old fashioned way:
> > xx <- c(NA,x)
> > modl <- lm(y~xx[1:length(y)])
> > summary(modl)
>
>One sidenote is that summary does not include any mention of the fact 
>that 1 observation was lost due to missing value. That seems bad to me.
>
>I see the lag function in ts, but when I use it, it doesn't change x, so
>
>obviously I don't see the point of that.
>
> > z <- lag (x)
> > z
>  [1] 1 3 1 3 1 3 1 3 4 4
>
>
>So long, thanks in advance, greetings, etc...
>
>-- 
>Paul E. Johnson                       email: pauljohn at ukans.edu
>Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
>University of Kansas                  Office: (785) 864-9086
>Lawrence, Kansas 66045                FAX: (785) 864-5700
>
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