Converting code to R Question

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
Of Jeremy Miles
Sent: Monday, February 25, 2013 5:41 PM
To: Craig J
Cc: r-help
Subject: Re: [R] Converting code to R Question

Here's a direct translation:
 Variable <- 0
 Variable <- ifelse(item1 == 1, Variable +1, Variable)
 Variable <- ifelse(item2 == 1, Variable +1, Variable)
 Variable <- ifelse(item3 == 1, Variable +1, Variable)
 Variable <- ifelse(item4 == 1, Variable +1, Variable)

Here's another way to do it:

Variable <- 0 + (item1 == 1) + (item2 == 1) + (item3 == 1) + (item4 == 1)

Note that I haven't worried about missing data - do you have NAs in
your items? If you do, and you want NA to be not equal to 1 (rather
than equal to NA):

Variable <- sum((item1 == 1), (item2 == 1) , (item3 == 1) , (item4 ==
1), na.rm=TRUE)


Jeremy


On 25 February 2013 17:02, Craig J <cjohns38 at gmail.com> wrote:

I'm learning R and am converting some code from SPSS into R.  My background
is in SAS/SPSS so the vectorization is new to me and I'm trying to learn
how to NOT use loops...or use them sparingly.  I'm wondering what the
most efficient to tackle a problem I'm working on is. Below is an example
piece of code.  Essentially what it does is set a variable to zero, loop
through item responses, and add one if a condition is met. For example, if
item one was responded as a 1 then add one to the final variable.  If item
two was responded as a 2 then add one to the final variable.  I have to do
this for five scales with each scale having 6 items half of which may have
the 1 response pattern and half the 2 pattern.

Any suggestions on how best to tackle this in R would be helpful.

Craig

**********
Old SPSS code sample
**********

Compute Variable = 0.

IF (item1 = 1) Variable = Variable +1 .

IF (item2= 2) Variable = Variable +1 .

IF (item3 = 1) Variable = Variable +1.

IF (item4 = 2) Variable = Variable +1.

EXECUTE .

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