replace function examples

Question

I don t find the help page for the replace function from the base package to be very helpful  Worst part  it has no examples which could help understand how it works   Could you please explain how to use it  An example or two would be great

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You can also use logical tests      x  lt - data frame a   c 0 1 2 NA   b   c 0 NA 1 2   c   c NA  0  1  2    x x a  lt - replace x a  is na x a   0  x x b  lt - replace x b  x b  2  333

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If you look at the function  by typing it s name at the console  you will see that it is just a simple functionalized version of the   lt - function which is described at         is a rather basic function to R so you would be well-advised to look at that page for further details  Especially important is learning that the index argument  the second argument in replace can be logical  numeric or character classed values  Recycling will occur when there are differing lengths of the second and third arguments   You should  read  the function call as   within the first argument  use the second argument as an index for placing the values of the third argument into the first     gt  replace  1 20  10 15  1 2    1   1  2  3  4  5  6  7  8  9  1  2  1  2  1  2 16 17 18 19 20   Character indexing for a named vector    gt  replace c a 1  b 2  c 3  d 4    b   10   a  b  c  d   1 10  3  4    Logical indexing    gt  replace x  lt - c a 1  b 2  c 3  d 4   x gt 2  10   a  b  c  d   1  2 10 10

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Be aware that the third parameter  value  in the examples given above  the value is a constant  e g   Z  or c 20 30      Defining the third parameter using values from the data frame itself can lead to confusion    E g  with a simple data frame such as this  using dplyr  data frame    tmp  lt - data frame a 1 10  b sample LETTERS 24 26   10  replace T     This will create somthing like this           a     b     int   chr  1      1     X 2      2     Y 3      3     Y 4      4     X 5      5     Z     etc  Now suppose you want wanted to do  was to multiply the values in column  a  by 2  but only where column  b  is  X   My immediate thought would be something like this   with tmp  replace a  b   X   a 2     That will not provide the desired outcome  however  The a 2 will defined as a fixed vector rather than a reference to the  a  column  The vector  a 2  will thus be    1   2  4  6  8 10 12 14 16 18 20   at the start of the  replace  operation  Thus  the first row where  b  equals  X   the value in  a  will be placed by 2  The second time  it will be replaced by 4  etc     it will not be replaced by two-times-the-value-of-a in that particular row

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Here s an example where I found the replace    function helpful for giving me insight  The problem required a long integer vector be changed into a character vector and with its integers replaced by given character values      figuring out replace     test  lt - c rep 1 3  rep 2 2  rep 3 1      which looks like    1  1 1 1 2 2 3   and I want to replace every 1 with an A and 2 with a B and 3 with a C  letts  lt - c  A   B   C     so in my own secret little  dirty-verse  I used a loop  for i in 1 3   test  lt - replace test test  i letts i      which did what I wanted  test  1   A   A   A   B   B   C    In the first sentence I purposefully left out that the real objective was to make the big vector of integers a factor vector and assign the integer values  levels  some names  labels    So another way of doing the replace    application here would be   test  lt - factor test labels letts    1  A A A B B C Levels  A B C

User · Answer

Here s two simple examples   gt  x  lt - letters 1 4   gt  replace x  3   Z    replacing  c  by  Z   1   a   b   Z   d   gt    gt  y  lt - 1 10  gt  replace y  c 4 5   c 20 30     replacing 4th and 5th elements by 20 and 30   1   1  2  3 20 30  6  7  8  9 10

[r] "replace" function examples

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