[R] creating variable that codes for the match/mismatch between two other variables

[PIKAL Petr]

Hi

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Jonas Walter
> Sent: Monday, February 25, 2013 2:38 PM
> To: r-help at r-project.org
> Subject: [R] creating variable that codes for the match/mismatch
> between two other variables
> 
> 
> 
> Dear all,
> 
> I have got two vectors coding for a stimulus presented in the current
> trial (mydat$Stimulus) and a prediction in the same trial
> (mydat$Prediciton), respectively.
> By applying an if-conditional I want to create a new vector that
> indicates if there is a match between both vectors in the same trial.
> That is, if the prediction equals the stimulus.
> 
> When I pick out some trials randomly, I get some trials with no match
> (mydat$Stimulus[1] != mydat$Prediction[1]) as well as some trials with
> a match (mydat$Stimulus[1] == mydat$Prediction[1]).
> 
> However, if I apply the following code, each trial is coded as a match.
> Why, what do I wrong?
> 
> In some blocks, there was no prediction recorded. Therefore, I want
> those trials to be labeled differently [that is, match = 7].
> 
> Coding-legend:
> 
> 1 = match
> 0 = no match
> 7 = no prediction recorded
> 
> The code:
> 
> # create varialbe that codes match/mismatch of prediction vs. stimulus
> 
> mydat$match <- 0
> 
> for (i in seq_along(1:nrow(mydat))) {
>  # if there is a match, mydat$match[i] = 1
        if
> (mydat$Stimulus[i] == mydat$Prediction[i]) {
>                 mydat$match = 1
> # the next to conditions refer to blocks without prediction recording.
> Therefore, the corresponding trials are coded with mydat$match[i] = 7.

> } else if (mydat$BlockOrder[i] == 1 & mydat$Block_nr[i] == 1) {
>                 mydat$match = 7
>         } else if (mydat$BlockOrder[i] == 2 & mydat$Block_nr[i] == 4) {
>                 mydat$match == 7
>         }
> }

Well, why so complicated?

(mydat$Stimulus == mydat$Prediction)*1

gives you vector of 1 when there is match and 0 when there is no match. 

I do not understand your no prediction though. How is no prediction coded? If NA, the resulting vector will have NA in corresponding item too.

Regards
Petr 


> 
> # The corresponding dataframe structure:
> 
> str(mydat)
> 'data.frame':   9302 obs. of  18 variables:
> $ BlockOrder       : int  1 1 1 1 1 1 1 1 1 1 ...
> $ Block_nr         : num  1 1 1 1 1 1 1 1 1 1 ...
> $ Trial_nr         : int  1 2 3 4 5 6 7 8 9 10 ...
> $ PreSeq.Length    : int  1 2 2 1 1 2 0 2 2 2 ...
> $ PreSeq           : int  21 12 21 20 20 12 0 21 22 11 ...
> $ Sequence         : int  121111 121212 121111 121111 112212 121221
> 121111 121111 122112 121111 ...
> $ Category         : int  2 1 3 2 1 1 3 3 1 3 ...
> $ FixCross.Latency : int  1429 1043 1093 1297 1155 1449 1140 1396 1341
> 1427 ...
> $ Stimulus         : int  2 1 2 2 1 1 1 1 2 1 ...
> $ RT               : int  333 275 378 428 442 388 340 394 414 542 ...
> $ RT.Button_pressed: int  2 1 2 2 1 1 1 1 2 1 ...
> $ RT.Accuracy      : int  1 1 1 1 1 1 1 1 1 1 ...
> $ Prediction       : int  0 0 0 0 0 0 0 0 0 0 ...
> $ Confidence       : int  0 0 0 0 0 0 0 0 0 0 ...
> $ ITI              : int  1053 1182 1467 1431 1103 1170 1232 1393 1356
> 1495 ...
> $ Subject          : num  4 4 4 4 4 4 4 4 4 4 ...
> $ ITruns           : num  0 0 0 1 0 1 2 3 0 0 ...
> $ match            : num  1 1 1 1 1 1 1 1 1 1 ...
> 
> # mydat$match, the new variable, only contains ones.
> 
> min(mydat$match)
> [1] 1
> > max(mydat$match)
> [1] 1
> 
> # example: row 1699: no match Stimulus - Prediction
> 
> mydat$Stimulus[1699] == mydat$Prediction[1699] # [1] FALSE
> 
> # but:
> 
> mydat$match[1699]
> # [1] 1
> 
> How can I get the right coding? Where is the mistake?
> 
> Thanks!
> 
> Best,
> Jonas Walter
> 
> 
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> 
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