How to find maximum string length by column in data frame

Question

My question is similar to this. But for strings.

So I have a dataframe, each column contains strings of different length. So, how I can find the maximum string length per column?

Then, how to select the columns, where length is > 1, by sapply or similar.

A typical column of the dataframe looks like this:

clmn=c("XDX", "GUV", "FQ", "ACUE", "HIT", "AYX", "NFD", "AHBW", "GKQ", "PYF")

Thanks

Answer 1

We can use nchar

max(nchar(clmn))

For finding the maximum character length for each column

lapply(df1, function(x) max(nchar(x)))

---

If we need to filter the columns that have maximum string length greater than 1

df1[sapply(df1, function(x) max(nchar(x)))>1]

Or

Filter(function(x) max(nchar(x)) >1, df1)

Answer 2

Here's a purrr::map() and stringr::str_length() solution.

dat <- structure(list(name = c("Luke Skywalker", "C-3PO", "R2-D2",
                               "Darth Vader", "Leia Organa", "Owen Lars"),
                      skin_color = c("fair", "gold", "white, blue", 
                                     "white", "light", "light"),
                      eye_color = c("blue", "yellow", "red", 
                                    "yellow", "brown", "blue"),
                      len_1 = c("A", "A", "A", "A", "A", "A")),
                 row.names = c(NA, -6L), class = c("tbl_df", "tbl", "data.frame"))

purrr::map(dat, ~max(stringr::str_length(.x)))
dat[names(which(purrr::map(dat, ~max(stringr::str_length(.x))) > 1))]