select rows with unidentical column values using R

Question

Hi Guys, I need to create a new data frame that excludes dams that appear in "dam1" and "dam2" columns on the same fosdate (fostering date). I tried df <- df[df$dam1!=df$dam2,] but did not work. Dam1 and dam2 are factors which are the id's of mothers.

my df:

fosdate      dam1     dam2
8/09/2009    2Z523    2Z523
30/10/2009   1W509    5C080
30/10/2009   1W509    5C640
30/10/2009   1W509    1W509
1/10/2009    1W311    63927

The new data frame that I need to get is: dfnew:

fosdate      dam1     dam2
30/10/2009   1W509    5C080
30/10/2009   1W509    5C640
1/10/2009    1W311    63927

Would appreciate any help!

Bazon

Answer 1

Wild guess based on the idea that you might be using R (since your other questions are about R). Note that I don't know R, I'm just putting 2 and 2 together from the other questions and answers given.

Try

df <- df[df$dam1 != df$dam2,]

i.e. specifiy df$ explicitly on both sides of the comparison clause.

Answer 2

My guess is that when you imported the data, df$dam1 and df$dam2 became factors

You can check this with

is.factor(df$dam1)

If this is the TRUE, then try something like

df[as.character(df$dam1) != as.character(df$dam2),]

Answer 3

The problem is that dam1 and dam2 are factors each with a different number of levels. To get around this you need to convert the factors to "characters" to do that comparison.

dfnew <-df[as.character(df$dam1) != as.character(df$dam2), ]