How to match characters change in R - r

Question

I have below-mentioned dataframe in R:
ID source_field_1 field_1 source_field_3 field_3
ER-1 AC45U CD34I 1992-01-23 23/01/1992
ER-2 AB15X 1971-01-23 23/1/1971
ER-3 DB22U AC22Z 1962-11-13 3/11/1962
ER-4 CF12R BA23D 1992-01-23 23/01/1992
I need a group by count of change of characters from column source_field_1 to field_1, from A to Z and from 0 to 9.
Required Output:
source_field_1 A B C D E . . . Z
A 1
B 1
C 1 1
D 1
E
F 1
.
. 1
. 1
Z
Need the same structure for numerical characters as well for both field_1 and field_3.

Answer 1

df1 <- na.omit(df)
create <- function(from,to,nm)
{
s <- sprintf("[^%s]",paste0(nm,collapse = ""))
from <- unlist(strsplit(gsub(s,"",from),""))
to <- unlist(strsplit(gsub(s,"",to),""))
table(from,to)
}
create(df1$source_field_1,df1$field_1,0:9)
to
from 2 3 4
1 1 0 0
2 2 1 0
4 0 1 0
5 0 0 1
create(df1$source_field_1,df1$field_1,LETTERS)
to
from A B C D I Z
A 0 0 1 0 0 0
B 0 0 1 0 0 0
C 0 1 0 1 0 0
D 1 0 0 0 0 0
F 1 0 0 0 0 0
R 0 0 0 1 0 0
U 0 0 0 0 1 1

Answer 2

This is rather simple to achieve by splitting up each character and using the table function.
library(stringr)
df <- [your df]
out <- vector('list', nrow(df))
for(i in seq_along(out)){
#Split both columns
splitted_str <- str_split(unlist(df[i, c('source_field_1', 'field_1')]), '')
#Alternative in base R:
#gsub(LETTERS, '', unlist(df[i, c('source_field_1', 'field_1')]))
#convert to factors, "levels" will be used in our columns
splitted_str <- lapply(splitted_str, factor, levels = LETTERS)
#Create table. dnn sets the names shown for column/rows
out[[i]] <- table(splitted_str, dnn = c('source_field_1', 'field_1'))
}
note that i abuse the fact that factor(...) sets all values not in levels to NA, and by default table(...) excludes these in the table.
Obviously this could all be combined into a single line
out <- lapply(seq(nrow(df)),
function(x) table(lapply(str_split(unlist(df[i, c('source_field_1', 'field_1')]), ''), factor, levels = LETTERS), dnn = c('source_field_1', 'field_1'))
)