/Useful_R_commands

Reading in a file

objectname <- read.delim("filename.xls", sep="\t", header=TRUE)

Writing a file

write.table(objectname, file="filename.xls", sep="\t", quote=FALSE, col.names=TRUE, row.names=FALSE)

NOTE if there are row names just change the argument to TRUE.

Merging 2 dataframes

Usually to merge dataframes of the same dimensions based on a common column

objectname <- merge(object1, object2, by.x="NameofCommonColumn_in_object1", by.y="NameofCommonColumn_in_object2", all=TRUE)

Subsetting a dataframe to include or exclude columns

To include:

objectname <- subset(object_to_be_subsetted, select=c(columnA, columnB, columnC))

To exclude:

objectname <- subset(object_to_be_subsetted, select= -c(columnA, columnB, columnC))

Subsetting a dataframe based on a list

object <- [dataframe[dataframe[,#]%in%list,]

NOTE: "#" refers to the column number that shares the same values contained in the list