[R] Split strings based on multiple patterns

Gabor Grothendieck ggrothendieck at gmail.com
Sat Oct 15 13:50:28 CEST 2016


Replace newlines and colons with a space since they seem to be junk,
generate a pattern to replace the attributes with a comma and do the
replacement and finally read in what is left into a data frame using
the attributes as column names.

(I have indented each line of code below by 2 spaces so if any line
starts before that then it's been wrapped around by the email and
needs to be adjusted.)

  attributes <-
  c("Water temp", "Waterbody type", "Water pH", "Conductivity",
  "Water color", "Water turbidity", "Manmade", "Permanence", "Max water depth",
  "Primary substrate", "Evidence of cattle grazing", "Shoreline
Emergent Veg(%)",
  "Fish present", "Fish species")

  ugly2 <- gsub("[:\n]", " ", ugly)

  pat <- paste(gsub("([[:punct:]])", ".", attributes), collapse = "|")
  ugly3 <- gsub(pat, ",", ugly2)

  dd <- read.table(text = ugly3, sep = ",", strip.white = TRUE,
col.names = c("", attributes))[-1]


On Fri, Oct 14, 2016 at 7:16 PM, Joe Ceradini <joeceradini at gmail.com> wrote:
> Afternoon,
>
> I unfortunately inherited a dataframe with a column that has many fields
> smashed together. My goal is to split the strings in the column into
> separate columns based on patterns.
>
> Example of what I'm working with:
>
> ugly <- c("Water temp:14: F Waterbody type:Permanent Lake/Pond: Water
> pH:Unkwn:
> Conductivity:Unkwn: Water color: Clear: Water turbidity: clear:
> Manmade:no  Permanence:permanent:  Max water depth: <3: Primary
> substrate: Silt/Mud: Evidence of cattle grazing: none:
> Shoreline Emergent Veg(%): 1-25: Fish present: yes: Fish species: unkwn: no
> amphibians observed")
> ugly
>
> Far as I can tell, there is not a single pattern that would work for
> splitting this string. Splitting on ":" is close but not quite consistent.
> Each of these attributes should be a separate column:
>
> attributes <- c("Water temp", "Waterbody type", "Water pH", "Conductivity",
> "Water color", "Water turbidity", "Manmade", "Permanence", "Max water
> depth", "Primary substrate", "Evidence of cattle grazing", "Shoreline
> Emergent Veg(%)", "Fish present", "Fish species")
>
> So, conceptually, I want to do something like this, where the string is
> split for each of the patterns in attributes. However, strsplit only uses
> the 1st value of attributes
> strsplit(ugly, attributes)
>
> Should I loop through the values of "attributes"?
> Is there an argument in strsplit I'm missing that will do what I want?
> Different approach altogether?
>
> Thanks! Happy Friday.
> Joe
>
>         [[alternative HTML version deleted]]
>
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email: ggrothendieck at gmail.com



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