[R] Odp: Comparing 2 slopes of 2 regression lines
Petr PIKAL
petr.pikal at precheza.cz
Mon Apr 6 12:56:21 CEST 2009
Hi
r-help-bounces at r-project.org napsal dne 06.04.2009 12:28:35:
> Hello everyone,
> I would like to test two regression slopes:do they differ
significantly?The
> data and commands I've used so far:
> x<-8.5:32.5 #Vektor x
> y<-c( NA , NA , 5.67 , 6.53 , 6.83, 7.41 , 7.93 , 8.5 , 8.86, 9.46
, 9.
> 82 , 10 ,10.35 , 10.7 ,11.03 ,11.37 ,11.61 ,11.84, 12.12, 12.39 ,12.67
,12.
> 96, 13.28 ,13.47, 13.65) #Vektor y
>
> (regression<-lm(y~x))
> summary(regression) Regression model 1
>
> x<-8.5:32.5 #Vektor x
> y<-c( NA, 5.88 ,6.95 , 7.2 ,7.66 , 8.02, 8.44, 9.06 , 9.65, 10.22
,10.
> 63, 11.06, 11.37, 11.91, 12.28 ,12.69 ,13.07 , 13.5 , 13.3 ,14.14 , NA
,
> NA , NA , NA , NA) #Vektor y
>
> (regression<-lm(y~x))
> summary(regression) Regression model 2
>
> Now I don't know how to continue as I want to test the slopes only ,not
the
> regression lines in total.
Here is one approach
http://tolstoy.newcastle.edu.au/R/e6/help/09/01/2632.html
>
> Another problem I have is rather a formal one:
> y<-c( NA , NA , 5.67 , 6.53 , 6.83, 7.41 , 7.93 , 8.5 , 8.86, 9.46
, 9.
> 82 , 10 ,10.35 , 10.7 ,11.03 ,11.37 ,11.61 ,11.84, 12.12, 12.39 ,12.67
,12.
> 96, 13.28 ,13.47, 13.65) #Vektor y
>
> that is my y-vector; I always need to copy and paste this line
originating
> from:
> X8.5 X9.5 X10.5 X11.5 X12.5 X13.5 X14.5 X15.5 X16.5 X17.5
> SD24 NA NA 5.67 6.53 6.83 7.41 7.93 8.5 8.86 9.46
>
> X18.5 X19.5 X20.5 X21.5 X22.5 X23.5 X24.5 X25.5 X26.5 X27.5 X28.5
> 9.82 10 10.35 10.7 11.03 11.37 11.61 11.84 12.12 12.39 12.67
>
> X29.5 X30.5 X31.5 X32.5
> 12.96 13.28 13.47 13.65
You probably read SD24 from some source by read.delim which suppose the
first line is header and subsequent lines (in your case only one) are
data.
I would try to read it with header = FALSE option. You shall get data
frame with 2 lines and you could then use
t(your.reed.data)
to transpose it to more convenient form.
Or you can use
x <- your.read.data[1,]
y <- your.read.data[2,]
to get x, y.
Regards
Petr
> R always considers the original data as different variables(as matrix).
> I already tried: y<-as.vector(SD24)
> It doesn't work. SD24 is the object giving me the original data you
see.
>
>
> sorry for writing so long; hope it is clear what I wrote.
>
> Thanks for your efforts, Benedikt
>
> --
>
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