How to search for equal variables in rows (in a smart way) and store according rows as subsets?

r

Solution

The `rle` function is really handy for stuff like this. It takes an atomic vector and returns a `list` with elements `lengths` and `values`, where `lengths` contains the run length of each value in `values`.

Since the call to `cbind` in your example coerces the `test` column to `factor`, I first converted it to `numeric`:

a1 <- within(a1, test <- as.numeric(as.character(test)))

Then the result can be obtained in a nice (essentially) one-liner:

with(rle(a1$test),
    split(a1, rep(seq_along(lengths), lengths))[values == BZ & lengths >= n_BZ]
)

Problem

I have a huge data frame. One column is an integer ranging from 1 to 2. What I need is a way to look for continous rows with a number of certain values in this column, subset these rows and process them later into graphs. I attached a small example, which does at least some of the desired work: I am able to print out the subsets I am looking for. But two questions remain: - I guess there are way smarter methods in R then to apply a "for" loop over the complete data.frame. Any hints? - Which command do I have to put in where now the "print" command is to store the temporary data.frame? I guess I need a list due to the differing length of the subsets... I already had a look at aggregate or ddply, but could not come up with a solution. Any help is highly appreciated. ``` test<-c(rep(1,3),rep(2,5),rep(1,3),rep(2,3),rep(1,3),rep(2,8),rep(1,3)) letters<-c("a","b","c","d") a1<-as.data.frame(cbind(test,letters)) BZ<-2 #The variable to look for n_BZ=4 #The number of minimum appearences k<-1 # A variable to be used as a list item index in which the subset will be stored for (i in 2:nrow(a1)){ if (a1$test[i-1]!=BZ & a1$test[i]==BZ) # When "test" BECOMES "2" {t_temp<-a1[i,]} #... start writing a temporary array else if (a1$test[i-1]==BZ & a1$test[i]==BZ) # When "test" REMAINS "2" {t_temp<-rbind(t_temp,a1[i,])} #... continue writing a temporary array else if (a1$test[i-1]==BZ & a1$test[i]!=BZ) # When "test" ENDS BEING "2" {if (nrow(t_temp)>n_BZ) #... check if the temporary array has more rows then demanded {print(t_temp) #... print the array (desired: put the array to a list item k) k<-k+1}} #... increase k else # If array too small {t_temp<-NULL} # reset } ```

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