R help - Jul 2011 - Confusing piece of R code

m0<-epxression((4*theta1*theta2-theta3^2)/(2*x*theta3^2)-0.5*theta1*x)

params<-all.vars(m0)                              this reads all the params
from m0 so theta1,2 and 3 correct?
params<-params[-which(params=="x")]      checks which params are
multiplied
by x?
np<-length(params)                                

for(i in 1:6){
esp<-get(sprintf("m%d",i-1))                    what does get do?
sprinf
formats strings? so what is it doinf here?
assign(sprintf("m%d",i),D(esp,"x"))             what doeas
assign so what in
sprintf doing and what does D do?
}

really really confused?

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Have you looked at the manual for any of these? 

?get
?sprintf
?assign 
#and so on...




?
Bazman76 wrote:
> 
> m0<-epxression((4*theta1*theta2-theta3^2)/(2*x*theta3^2)-0.5*theta1*x)
> 
> params<-all.vars(m0)                              this reads all the
> params from m0 so theta1,2 and 3 correct?
> params<-params[-which(params=="x")]      checks which params
are
> multiplied by x?
> np<-length(params)                                
> 
> for(i in 1:6){
> esp<-get(sprintf("m%d",i-1))                    what does get
do? sprinf
> formats strings? so what is it doinf here?
> assign(sprintf("m%d",i),D(esp,"x"))             what
doeas assign so what
> in sprintf doing and what does D do?
> }
> 
> really really confused?
> 

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The neat thing about R is that it's interpreted, so you can look for
yourself.

On Sat, Jul 9, 2011 at 3:46 PM, Bazman76 <h_a_patience at hotmail.com>
wrote:
> m0<-epxression((4*theta1*theta2-theta3^2)/(2*x*theta3^2)-0.5*theta1*x)
>
> params<-all.vars(m0) ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?this reads all the
params
> from m0 so theta1,2 and 3 correct?
> m0<-expression((4*theta1*theta2-theta3^2)/(2*x*theta3^2)-0.5*theta1*x)
> params<-all.vars(m0)
> params
[1] "theta1" "theta2" "theta3" "x"

So no, not just the thetas but also x

> params<-params[-which(params=="x")] ? ? ?checks which params
are multiplied
> by x?
> params<-params[-which(params=="x")]
> params
[1] "theta1" "theta2" "theta3"

Nope, see that it takes out the params that are not equal to x. You
could look at, for instance ?which to figure that out, and also ?"=="
> np<-length(params)
>
> for(i in 1:6){
> esp<-get(sprintf("m%d",i-1)) ? ? ? ? ? ? ? ? ? ?what does get
do? sprinf
> formats strings? so what is it doinf here?
Again, you can try it.
> i <- 1
> sprintf("m%d",i-1)
[1] "m0"

So it's taking the value of i, and combining it with some other things
to make a character name. get() will get the R object with that name
and assign it to esp
?get will tell you that.
> assign(sprintf("m%d",i),D(esp,"x")) ? ? ? ? ? ? what
doeas assign so what in
> sprintf doing and what does D do?
> }
Same thing in reverse. I'll leave this one as an exercise for the querent.

Sarah
> really really confused?
Learning to try things and to read the help are the only cure.

Sarah

-- 
Sarah Goslee
http://www.functionaldiversity.org

thanks sarah


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