Sum rows in data frame or matrix

Question

I have a very large dataframe with rows as observations and columns as genetic markers  I would like to create a new column that contains the sum of a select number of columns for each observation using R   If I have 200 columns and 100 rows  I would like a to create a new column that has 100 rows with the sum of say columns 43 through 167   The columns have either 1 or 0  With the new column that contains the sum of each row  I will be able to sort the individuals who have the most genetic markers   I feel it is something close to   data new sum data   43 167

User · Answer

The rowSums function  as Greg mentions  will do what you want  but you are mixing subsetting techniques in your answer  do not use     when using       your code should look something more like   data new  lt - rowSums  data  43 167      If you want to use a function other than sum  then look at  apply for applying general functions accross rows or columns

User · Answer

I came here hoping to find a way to get the sum across all columns in a data table and run into issues implementing the above solutions  A way to add a column with the sum across all columns uses the cbind function    cbind data  total   rowSums data     This method adds a total column to the data and avoids the alignment issue yielded when trying to sum across ALL columns using the above solutions  see the post below for a discussion of this issue    Adding a new column to matrix error

User · Answer

you can use rowSums  rowSums data  should give you what you want

[r] Sum rows in data.frame or matrix

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