Same code, same data, different output.


I've been trying to run several hydrological models for my dissertation. Previously I had completed one model to an acceptable standard. Once I had finished that model I saved the code and shut R down for the night. The next morning I opened R and the ran the exact same code with the exact same input data and got a completely different result.
Does anyone know what has gone wrong here? I've been working on this code for weeks now but I haven't been getting the results I need... and I believe this problem is why. Any input would be appreciated.


One possibility springs to mind: if you have any code which uses random numbers, e.g. sample(), then you will get a different set of numbers each time the model is run unless you use set.seed().

Thanks for the reply. I don't use any random numbers in my code. Each time I run the code I get the same result. In fact, sometimes I try to change my input data and still get the same result as I did with the previous data. At this stage I don't know what to think. I am certain that I'm using the right files as well.

This could happen for a lot of reasons, most likely related with keeping old data in your environment while doing EDA and modeling. It's hard to know for sure without a reproducible example.

Could you ask this with a minimal REPRoducible EXample (reprex)? A reprex makes it much easier for others to understand your issue and figure out how to help.

This topic was automatically closed 21 days after the last reply. New replies are no longer allowed.

If you have a query related to it or one of the replies, start a new topic and refer back with a link.