Summarize and count data in R with dplyr

Question

Goal: Summarize/count responses in the same row of an occured stimuli with dplyr.

Background: I got some excellent help in another topic: Loop

Answer 1

Here is a two line solution in base R. First, create an ID that is unique to each user-(new)stimulus combination. This is accomplished with paste and cumsum.

dat$stims <- with(dat, paste(cumsum(StimuliA), cumsum(StimuliB), sep="_"))

Then use aggregate to calculate the responses for each of the new IDs

aggregate(. ~ User + stims, data=dat, sum)
  User stims StimuliA StimuliB R2 R3 R4 R5 R6 R7
1    1   1_0        1        0  0  0  0  0  0  1
2    1   2_0        1        0  1  1  0  0  1  0
3    1   2_1        0        1  1  2  0  0  1  0
4    1   2_2        0        1  0  0  0  0  0  0
5    2   3_2        1        0  3  0  0  0  0  0
6    2   3_3        0        1  1  0  0  0  2  0