Mean of a column in a data frame given the column s name

Question

I m inside a big function I have to write  In the last part I have to calculate the mean of a column in a data frame  The name of the column I am operating on is given as an argument to the function

User · Answer

Any of the following should work    df  lt - data frame x 1 3 y 4 6   mean df x  mean df  1   mean df   x

User · Answer

Use summarise in the dplyr package   library dplyr  summarise df  Average   mean col name  na rm   T     note  dplyr supports both summarise and summarize

User · Answer

I think you re asking how to compute the mean of a variable in a data frame  given the name of the column  There are two typical approaches to doing this  one indexing with    and the other indexing with     data iris  mean iris   Petal Length        1  3 758 mean iris   Petal Length       1  3 758 mean iris   Sepal Width        1  3 057333 mean iris   Sepal Width       1  3 057333

User · Answer

I think what you are being asked to do  or perhaps asking yourself    is take a character value which matches the name of a column in a particular dataframe  possibly also given as a character   There are two tricks here  Most people learn to extract columns with the     operator and that won t work inside a function if the function is passed a character vecor  If the function is also supposed to accept character argument then you will need to use the get function as well    df1  lt - data frame a 1 10  b 11 20   mean col  lt - function  dfrm  col   mean  get dfrm    col       mean col  df1    b       1  15 5   There is sort of a semantic boundary between ordinary objects like character vectors and language objects like the names of objects  The get function is one of the functions that lets you  promote  character values to language level evaluation  And the     function will NOT evaluate its argument in a function  so you need to use          only is useful at the console level and needs to be completely avoided in functions

User · Answer

Suppose you have a data frame say df  with columns  x  and  y   you can find mean of column  x or y  using   1 Using mean   function  z lt -mean df x    2 Using the column name say x  as a variable using attach   function   attach df   mean x    When done you can call detach   to remove  x   detach     3 Using with   function  it lets you use columns of data frame as distinct variables    z lt -with df mean x

User · Answer

if your column contain any value that you want to neglect  it will help you     da is data frame  amp  Ozone is column name     for single column mean da Ozone  na rm   TRUE       for all columns colMeans x da  na rm   TRUE

[r] Mean of a column in a data frame, given the column's name

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