Extracting numbers from vectors of strings

Question

I have string like this   years lt -c  20 years old    1 years old     I would like to grep only the numeric number from this vector  Expected output is a vector   c 20  1    How do I go about doing this

User · Answer

Using the package unglue we can do       install packages  unglue   library unglue   years lt -c  20 years old    1 years old   unglue vec years    x  years old   convert   TRUE    gt   1  20  1   Created on 2019-11-06 by the reprex package  v0 3 0   More info  https   github com moodymudskipper unglue blob master README md

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We can also use str extract from stringr  years lt -c  20 years old    1 years old   as integer stringr  str extract years     d       1  20  1   If there are multiple numbers in the string and we want to extract all of them  we may use str extract all which unlike  str extract returns all the macthes    years lt -c  20 years old and 21    1 years old   stringr  str extract years     d      1   20    1   stringr  str extract all years     d        1     1   20   21      2     1   1

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Update Since extract numeric is deprecated  we can use parse number from readr package   library readr  parse number years    Here is another option with extract numeric  library tidyr  extract numeric years    1  20  1

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Extract numbers from any string at beginning position   x  lt - gregexpr    0-9     years     Numbers with any number of digits x2  lt - as numeric unlist regmatches years  x      Extract numbers from any string INDEPENDENT of position   x  lt - gregexpr   0-9     years     Numbers with any number of digits x2  lt - as numeric unlist regmatches years  x

User · Answer

I think that substitution is an indirect way of getting to the solution  If you want to retrieve all the numbers  I recommend gregexpr   matches  lt - regmatches years  gregexpr     digit       years   as numeric unlist matches     If you have multiple matches in a string  this will get all of them  If you re only interested in the first match  use regexpr instead of gregexpr and you can skip the unlist

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After the post from Gabor Grothendieck post at the r-help mailing list  years lt -c  20 years old    1 years old    library gsubfn  pat  lt -   -  e0-9    d  sapply years  function x  strapply x  pat  as numeric   1

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You could get rid of all the letters too    as numeric gsub     alpha          years     Likely this is less generalizable though

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A stringr pipelined solution   library stringr  years   gt   str match all   0-9       gt   unlist   gt   as numeric

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Or simply   as numeric gsub    D       years      1  20  1

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Here s an alternative to Arun s first solution  with a simpler Perl-like regular expression   as numeric gsub      d         years  perl TRUE

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How about    pattern is by finding a set of numbers in the start and capturing them as numeric gsub    0-9            1   years     or    pattern is to just remove  years old as numeric gsub   years old       years     or    split by space  get the element in first index as numeric sapply strsplit years              1

[regex] Extracting numbers from vectors of strings

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