[R] For loop with i and j and multiple if statements... help!
ingaschwabe
ingaschwabe at gmail.com
Thu Oct 18 12:35:46 CEST 2012
Dear all!
I'm quite new to R and at this moment a little bit lost in trying to make a
function work with a for loop
that has two variables (i and j) and multiple if statements..
I hope that someone of you could help me. I would very appreciate it!
What do I want to do? I am analysing the data of an 'eye tracker'. The eye
tracker registers the coordinates to which participants looked while reading
a website.
The data looks like this:
Number x y
1 1 701 209
2 2 685 209
3 3 566 248
4 4 562 234
5 5 601 225
6 6 608 232
[....]
To assign look zones, I looked which zone (e.g. the references) is
represented by which coordinates. This give the following results:
Look zone 1 = x > 170, x < 1250, y > 150 and y < 480
look sone 2 = x > 170, x < 420, y > 480 and y < 810.
Now I would like to assign a lookzone for each subject by the means of a
function with a for loop.
I've made this:
lookzones <- function(input){
lookzone <- matrix(0, nrow(input), 1)#Make space for
lookzone variables
for(i in 1:nrow(input)){
for(j in 1:nrow(input)){
if (x[i] > 170 && x[i] < 1250 && x[j] > 150 && y[j] < 480)
{lookzone <- 1}
if (x[i] > 170 && x[i] < 420 && x[j] > 480 && y[j] < 810)
{lookzone <- 2}
}
list(lookzone = lookzone)
input <- cbind(input, lookzone)
}
}
First, there is a variable made (lookzone) in which the values of the
lookzones can be stored. Then in the for loop, it is tested whether all
conditions are met (see above) and then a value is assigned to the lookzone
variable.
The input variable is a data set that looks like the data above.
However, the function does not seem to work.
When I run it, R assigns a value '1' to every x/y combination.
Can someone help me with this?
Thank you so much !
Bye, inga
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