I am aware that how to convert a vector layer to a raster layer is a quite frequent problem and that there are many questions and answers dealing with it. However, none was helpful concerning my specific problem, so I hope it's okay to ask again. I have a huge dataset consisting of fish catch data - different species and the location where they were caught. The original data is a csv file, but I'm working with it in QGIS and have created a vector file from the spreadsheet. Now I want to use another program (Zonation) that only accepts raster files to calculate species richness in certain areas - is there a possibility to create a raster from a vector layer with irregular points? I have tried the Rasterize tool, but it only gives me a solid rectangle and all individual data points are lost. I'm working with CRS WGS 84 and I have tried to set the cell size to 0.4, but still it's only one solid square. I've never worked with raster files before and I'm very grateful for your help - thanks!
It is not clear from your question what format the "other program" expects. 1) A "binary" raster with the value of the catch in cells with recordedcatch, and zeros elsewhere? 2) A raster with interpolated values of fish catch? Or 3) something else?
Case 3: You need to provide somemore details, but you might end up with one of the tools described above.
For general vector->raster operations, see How to convert a vector layer to raster?.
I guess your procedure was correct and can be improved with previous answers.
To avoid your previous results, obtain beforehand the distance between your points in degrees (since you are using geographic coordinates) and use less than that length as cell size to avoid that two values falls in one cell and losing data.
Remember that 1 degree is ~111 km in the Equator, then 0.4 degrees of cell size as you choose is around 44.4 km x 44.4 km. If your sampling area is equal or smaller than that you will get 1 single cell.
Try using a smaller cell size (0.009 is around 1 km in the Equator but you should check your data latitude').
Or you can reproject your data to UTM to use meters as input in cell size.
I hope this helps for someone with the same problem.