[R] “For” calculation is so slow

[Petr PIKAL]

Hi

> 
> Dear All,
> 
> The function I wrote can run well with the small data, but with the 
large
> data, the function runs very very slowly. How can I correct it? Thank 
you

Your function does not run slowly, it does not run at all.

> l(10,20)
Error in l(10, 20) : object 's' not found

No s object found. I presume that also gx and gy will not be found.

And besides I am pretty sure that you probably does not need any loop at 
all.

> very much. My function as below:
> 
> a<-c(1:240)
> b<-c(1:240)
> l=function(a,b){
> v=0
> u=0
> uv=0
> v[1]=0

Why?

v<-0
v
[1] 0
v[1]<-0
v
[1] 0

So there is no difference between first "v" and second "v"


> u[1]=0
> uv[1]=0
> for (i in 1:(length(s)-1)){
> 
v[i]<-((gx[[i]][b,(gx[[i]][a,1]+1)])-(gx[[i]][a,gx[[i]][a,1]+1]))/(gx[[i]]
> [a,gx[[i]][a,1]+1])
> 
u[i]<-((gy[[i]][a,(gy[[i]][a,1]+1)])-(gy[[i]][b,gy[[i]][a,1]+1]))/(gy[[i]]
> [a,gy[[i]][a,1]+1])
> uv[i]<-v[i]+u[i]
> }
> w=0
> w=mean(uv)

Your function does not return anything. Here you can test it by yourself 
on shortened version

l=function(a,b){
v=0
u=0
uv=0
v<-10
u<-20
uv<-v+u
w=0
w=mean(uv)
}

Regards
Petr





> }
> kk<-data.frame()
> for (a in 1:240){
> for (b in 1:240){
> if (a<b)
> kk[a,b]=l(a,b)
> else kk[a,b]=0
> }}
> max(kk)
> 
> 
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> calculation-is-so-slow-tp4630830.html
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> 
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