Greetings,
I confess to being new to R, which I am exploring for some simulation
modeling purposes. I am a long time programmer in PHP.
I am having some trouble getting over the "steep learning curve" with
some very basic things which are probably just little "a-ha" things in
R. I have hunted and hunted through the manual and cannot figure this
one out, so I am appealing for help.
I have the following program:
results <- replicate(10000,0)
for (year in 2000:2050) {
print(year);
for (i in 1:10000) {
x=results[i];
if (x == 0) {
prev = results[i-1];
next = results[i+1];
prob=0.1;
if (i>=1) {
if (prev==1) { prob=prob+0.4; }
}
if (i<10000) {
if (next==1) { prob=prob+0.4; }
}
y=runif(1,0,1);
if (y<prob) { x=1; }
results[i]=x;
}
}
}
No matter how I try this (and I've tried a number of variations), I
get an error similar to
Error in next = results[i + 1] : invalid (NULL) left side of assignment
I need to be able to loop through the results vector and compare the
previous/next items in the list to the current one. Is that possible?
What am I missing?
Cordially,
Justin Long
Getting a vector result from a computed index
2 messages · Justin Long, Ben Tupper
Hi,
On Mar 22, 2013, at 11:09 PM, Justin Long wrote:
Greetings,
I confess to being new to R, which I am exploring for some simulation
modeling purposes. I am a long time programmer in PHP.
I am having some trouble getting over the "steep learning curve" with
some very basic things which are probably just little "a-ha" things in
R. I have hunted and hunted through the manual and cannot figure this
one out, so I am appealing for help.
I have the following program:
results <- replicate(10000,0)
for (year in 2000:2050) {
print(year);
for (i in 1:10000) {
x=results[i];
if (x == 0) {
prev = results[i-1];
next = results[i+1];
prob=0.1;
if (i>=1) {
if (prev==1) { prob=prob+0.4; }
}
if (i<10000) {
if (next==1) { prob=prob+0.4; }
}
y=runif(1,0,1);
if (y<prob) { x=1; }
results[i]=x;
}
}
}
No matter how I try this (and I've tried a number of variations), I
get an error similar to
Error in next = results[i + 1] : invalid (NULL) left side of assignment
I need to be able to loop through the results vector and compare the
previous/next items in the list to the current one. Is that possible?
What am I missing?
I'm not very clear on what you are trying in the above code block, but comparing neighbor values is very easy. n <- 10 x <- floor(runif(n, min = 1, max = 10)) dx <- diff(x)
x
[1] 6 3 2 4 8 8 2 2 4 2
dx
[1] -3 -1 2 4 0 -6 0 2 -2 Is that what you are aiming for? Also, 'next' is a reserved word in R, that might be why an error is raised. See ?next Even if you could get past that, you'll get unexpected results if the index [i-1] falls to less than 1 or the index [i+1] rises to greater than the length of results.
x[0]
numeric(0)
x[101]
[1] NA Cheers, Ben Ben Tupper Bigelow Laboratory for Ocean Sciences 60 Bigelow Drive, P.O. Box 380 East Boothbay, Maine 04544 http://www.bigelow.org