如何搜索多个字符串并将其替换为字符串列表中的任何内容

Question

I have a column in a dataframe like this:

npt2$name
#  [1] "Andreas Groll, M.D."
#  [2] ""
#  [3] "Pan-Chyr Yang, PHD"
#  [4] "Suh-Fang Jeng, Sc.D"
#  [5] "Mostafa K Mohamed Fontanet Arnaud"
#  [6] "Thomas Jozefiak, M.D."
#  [7] "Medical Monitor"
#  [8] "Qi Zhu, MD"
#  [9] "Holly Posner"
# [10] "Peter S Sebel, MB BS, PhD Chantal Kerssens, PhD"
# [11] "Lance A Mynderse, M.D."
# [12] "Lawrence Currie, MD"

I tried gsub but with no luck. After doing toupper(x) I need to replace all instances of 'MD' or 'MD' or 'PHD' with nothing.

Is there a nice short trick to do it?

In fact I would be interested to see it done on a single string and how differently it is done in one command on the whole list.

Answer 1

Either of these:

gsub("MD|M\\.D\\.|PHD", "", test)  # target specific strings
gsub("\\,.+$", "", test)        # target all characters after comma

Both Matt Parker above and Tommy below have raised the question whether 'MRCP', 'PhD', 'D.Phil.' and 'Ph.D.' or other British or Continental designations of doctorate level degrees should be sought out and removed. Perhaps @user56 can advise what the intent was.

Answer 2

With a single ugly regex:

 gsub('[M,P].?D.?','',npt2$name)

Which says, find characters M or P followed by zero or one character of any kind, followed by a D and zero or one additional character. More explicitly, you could do this in three steps:

npt2$name <- gsub('MD','',npt2$name)
npt2$name <- gsub('M\\.D\\.','',npt2$name)
npt2$name <- gsub('PhD','',npt2name)

In those three, what's happening should be more straight forward. the second replacement you need to "escape" the period since its a special character.

Answer 3

Here's a variant that removes the extra ", " too. Does not require touppper either - but if you want that, just specify ignore.case=TRUE to gsub .

test <- c("Andreas Groll, M.D.", 
  "",
  "Pan-Chyr Yang, PHD",
  "Suh-Fang Jeng, Sc.D",
  "Peter S Sebel, MB BS, PhD Chantal Kerssens, PhD",
  "Lawrence Currie, MD")

gsub(",? *(MD|M\\.D\\.|P[hH]D)", "", test)
#[1] "Andreas Groll"                         ""                                     
#[3] "Pan-Chyr Yang"                         "Suh-Fang Jeng, Sc.D"                  
#[5] "Peter S Sebel, MB BS Chantal Kerssens" "Lawrence Currie"