R - Nested loops for specific values in vectors

user_13229209 0
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I'm pretty new to loops in R/in general and couldn't find an answer elsewhere.

I am using a nested loop to paste values of two vectors into a hyperlink. While I would like to only have three output strings, I am receiving nine strings in total. Maybe this is really easy, but any input is highly appreciated. 

**Example:** 

start <- c("Value1", "Value2", "Value3")
end <- c("Value1.1", "Value2.1", "Value3.1")

summary <- c()

for (i in start) {
    for(j in end) {

  summary[i] <- print(paste('This is a Hyperlink Text', 
  i, 'here it continues', j ,'here it ends'))
    }  
}

**Actual Output:** 

[1] "This is a Hyperlink Text **Value1** here it continues **Value1.1** here it ends"
[1] "This is a Hyperlink Text **Value1** here it continues **Value2.1** here it ends"
[1] "This is a Hyperlink Text **Value1** here it continues **Value3.1** here it ends"
[1] "This is a Hyperlink Text **Value2** here it continues **Value1.1** here it ends"
[1] "This is a Hyperlink Text **Value2** here it continues **Value2.1** here it ends"
[1] "This is a Hyperlink Text **Value2** here it continues **Value3.1** here it ends"
[1] "This is a Hyperlink Text **Value3** here it continues **Value1.1** here it ends"
[1] "This is a Hyperlink Text **Value3** here it continues **Value2.1** here it ends"
[1] "This is a Hyperlink Text **Value3** here it continues **Value3.1** here it ends"


**Desired ouput:** 

"This is a Hyperlink Text **Value1** here it continues **Value1.1** here it ends"
"This is a Hyperlink Text **Value1** here it continues **Value2.1** here it ends"
"This is a Hyperlink Text **Value1** here it continues **Value3.1** here it ends"
r loops
3 Answers

Your nested loop isn't necessary if the values have the same index. The way it's set up is necessarily giving you i x j rows. So, here, using only one index, single loop:

for (i in 1:length(start)) {
  summary[i] <- print(paste('This is a Hyperlink Text', 
                              start[i], 'here it continues', end[i]  ,'here it ends'))
user_41142400 
mapply(function(x, y) paste('This is a Hyperlink Text', x, 'here it continues', y ,'here it ends'), 
       x = start, y = end)

#                                                                    Value1 
# "This is a Hyperlink Text Value1 here it continues Value1.1 here it ends" 
#                                                                    Value2 
# "This is a Hyperlink Text Value2 here it continues Value2.1 here it ends" 
#                                                                    Value3 
# "This is a Hyperlink Text Value3 here it continues Value3.1 here it ends"
user_16917230

How about like this?

start <- c("Value1", "Value2", "Value3")
end <- c("Value1.1", "Value2.1", "Value3.1")

summary <- c()
for (i in seq_along(start)) {
    summary[i] <- paste('This is a Hyperlink Text', 
                              start[i], 'here it continues', end[i] ,'here it ends')
}
print(summary)

Or with an apply function that takes two vectors as input from purrr.

library(purrr)
purrr:::map2(start,end,~ paste('This is a Hyperlink Text', .x, 'here it continues', .y ,'here it ends'))
user_130953260
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