how to rearrange an order of matches between two data frames

Question

I have been busy with this question since last night and I could not figure out how to do it.

What I want to do is to match df1 strings to df2 strings and get the s

Answer 1

In this case I find it easier to switch the data to the wide format and before merging it to the lookup table.

You could try:

library(tidyr)
library(dplyr)
df1_tmp <- df1
df2_tmp <- df2
#add numerical id to df1_tmp to keep row information
df1_tmp$id <- seq_along(df1_tmp[,1])

#switch to wide and unnest rows with several strings
df1_tmp <- gather(df1_tmp,key="s_val",value="query_string",-id)
df1_tmp <- df1_tmp %>% 
        mutate(query_string = strsplit(as.character(query_string), ";")) %>% 
        unnest(query_string)


df2_tmp$IDs. <- gsub("[()]", "", df2_tmp$IDs.)

#add numerical id to df1_tmp to keep row information
df2_tmp$id <- seq_along(df2_tmp$IDs.)

#unnest rows with several strings
df2_tmp <- df2_tmp %>% 
        mutate(IDs. = strsplit(as.character(IDs.), ",")) %>% 
        unnest(IDs.)

res <- merge(df1_tmp,df2_tmp,by.x="query_string",by.y="IDs.")

res$ID_col_n <- paste(paste0(res$id.x,res$s_val))
res$total_id <- 1:nrow(res)
res <- spread(res,s_val,value=query_string,fill=NA)
res
#summarize to get required output 

res <- res %>% group_by(id.y) %>%
        mutate(No=n())  %>% group_by(id.y,No) %>%
        summarise_each(funs(paste(.[!is.na(.)],collapse=","))) %>% 
        select(-id.x,-total_id)

colnames(res)[colnames(res)=="id.y"]<-"IDs"

res$df1_colMatch_counts <- rowSums(res[,-(1:3)]!="")
df2_counts <- df2_tmp %>% group_by(id) %>% summarize(df2_string_counts=n())
res <- merge(res,df2_counts,by.x="IDs",by.y="id")
res


res

  IDs No    ID_col_n            s1     s2 df1_colMatch_counts df2_string_counts
1   1  1         4s1        P41182                          1                 2
2   2  1         4s1        P41182                          1                 2
3   3  1         4s1        P41182                          1                 2
4   4  3 2s2,3s1,5s1 Q9Y6Q9,Q09472 Q92831                   2                 4
5  15  1         3s2               P54612                   1                 5
6  16  1         7s2               O15143                   1                 7