At 09:47 PM 2/22/2005 -0500, Liaw, Andy wrote:
>Following the suggestions in the Posting Guide would help us to help you
>much better.
>
>What command(s) did you use to get the data into 
>R?   read.table("C:/.../persist.dat",col.names=c("a","b",etc."))


>What does the `.dat' file look like?  Itn was created in Word, as a plain 
>text file.

6000 24 female 0.0014 1.4 1 3.47 0.25 2478.57
6000 168 female 0.0014 1.4 1 0.73 0.05 521.43
6000 96 female 0.0014 1.4 1 0.96 0.07 685.71
6000 168 female 0.0014 1.4 1 1.36 0.10 971.43
6000 24 female 0.0014 1.4 1 2.69 0.19 1921.43
6000 96 female 0.0014 1.4 1 0.76 0.05 542.86...

>What are `x' and `y'?  'x' is "trt" and 'y' is "ppmtrans".  I did subset 
>commands to find all the males with "ppmsamp"
above a certain value.
>

persist[1:5,]
    dose     trt    sex      massg   massmg vol  ppm  perc ppmsamp
1  6000  24     female 0.0014    1.4         1   3.47  0.25 2478.57
2  6000  168  female 0.0014    1.4          1   0.73  0.05  521.43
3  6000  96    female 0.0014    1.4          1   0.96  0.07  685.71
4  6000  168  female 0.0014    1.4          1   1.36  0.10  971.43
5  6000  24    female 0.0014    1.4          1    2.69  0.19 1921.43
...subsetting commands...
ppmtrans<-sqrt(sqrt(ppm.male.mark$ppmsamp))
 > persist.male<-cbind(ppm.male.mark,ppmtrans)
 > persist.male[1:5,]
    dose trt  sex  massg massmg vol  ppm perc ppmsamp ppmtrans
27 6000  96 male 0.0012    1.2   1 1.82 0.15 1516.67 6.240549
55 6000 168 male 0.0012    1.2   1 0.90 0.08  750.00 5.233176
70 6000 168 male 0.0012    1.2   1 1.97 0.16 1641.67 6.365338
76 6000  96 male 0.0012    1.2   1 4.02 0.34 3350.00 7.607837
83 6000 168 male 0.0012    1.2   1 1.26 0.11 1050.00 5.692425
 > plot(trt,ppmtrans)
Error in model.frame(formula, rownames, variables, varnames, extras, 
extranames,  :
         variable lengths differ

After my initial post, I found that if I specified the data set in the plot 
arguments, I could generate a boxplot.  I then performed
ANOVA on the response after creating factor levels for "trt", and generated 
a stripchart showing the data in each of the three trts.  But for future 
reference, if I need to do linear regression with a similar data set, I'd 
like to know what is happening.

Thank you--

NH Ellis



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