You first need to calculate which 5x5 cell your individual data point falls into, then you can calculate the average per cell. In a simple example of just 5 data points, I am setting up a table that I *assume* to be similar to your data:

library(data.table)

thedata

Dear Dr Rittner,

I am trying to apply your script to my date but unfortunately it does not work.

The name of my dataset is "STT_DATASET"

when I try this:

SST_DATASET[,`:=`(cellx=5*(lon %/% 5)+2.5, celly=5*(lat %/% 5)+2.5)]

I receive this error:

Error in `:=`(cellx = 5 * (lon%/%5) + 2.5, celly = 5 * (lat%/%5) + 2.5) :

Check that is.data.table(DT) == TRUE. Otherwise, := and `:=`(...) are defined for use in j, once only and in particular ways. See help(":=").

Am i doing anything wrong?

Thank you in advance

Hi Diego Cepeda,

Try doing "class(STT_DATASET)". Does that return "data.table" / "data.frame"? That could be your problem as Martin said, his method is working on a data.table class object.

If you could post the first few lines of your dataframe so people could see exactly what it looks like (and the return of class()) that would be helpful.

I think this could be done with a simple apply function as well, but I'd like to see the format of the data before offering up code that might just be confusing.

Good luck!

Hi Diego,

As Kyle was pointing out, your data does not seem to be a data table. You could try converting with

SST_conv

thank you both!

@ Diego Cepeda,

It is to be made clear on whether you want to calculate the mean of each of the two variables of the mean of the two variables.