Convert vector of strings into a vector of objects-names

Question

Example Data:

a <- c("cat", "dog", "mouse")
b <- c("spoon", "fork", "knife")
c <- c("auto", "boot", "bike")

Generate Variables:

objects <-c(a,b,c)
strings <-c("a","b","c")

Give me the length of all strings:

> nchar(objects)
[1] 3 3 5 5 4 5 4 4 4

> nchar(strings)
[1] 1 1 1

What do i have to do to "strings" to give me the same result as "objects"?

The closest i have gotten so far:

> nchar(eval(parse(text=strings)))
[1] 4 4 4
>

But where is the rest?

I believe you want: nchar(unlist(lapply(strings,function(s) eval(parse(text=s))))) — aichao
– aichao, Commented Dec 5, 2016 at 15:42
Thank you. I will test your answers in my function and check the correct one if i get the result i want. — Andre Elrico
– Andre Elrico, Commented Dec 5, 2016 at 16:03
In case, you need a for loop, here is one v1 <- vector(); for(j in strings){ v1 <- c(v1, nchar(get(j))) } > v1 — akrun
– akrun, Commented Dec 5, 2016 at 16:16
@aichao. if you reply to my post i can set your comment as the answer. — Andre Elrico
– Andre Elrico, Commented Dec 6, 2016 at 16:07

akrun · Accepted Answer · 2016-12-05 15:42:27Z

3

We can use mget to return the values of the objects in a list, unlist it to a vector and get the nchar

nchar(unlist(mget(strings), use.names=FALSE))
#[1] 3 3 5 5 4 5 4 4 4

answered Dec 5, 2016 at 15:42

akrun

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Ronak Shah · Accepted Answer · 2016-12-05 15:49:57Z

2

One option is using sapply over each element of strings, get the value of element and calculate the number of characters with nchar

c(sapply(strings, function(x) nchar(get(x))))
#[1] 3 3 5 5 4 5 4 4 4

answered Dec 5, 2016 at 15:49

Ronak Shah

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aichao · Accepted Answer · 2016-12-06 16:12:59Z

1

The key is to loop over each element of strings and apply eval(parse(text=s)). Then unlist to a vector and call nchar:

nchar(unlist(lapply(strings,function(s) eval(parse(text=s)))))
##[1] 3 3 5 5 4 5 4 4 4

Hope this helps.

answered Dec 6, 2016 at 16:12

aichao

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