Summing numbers separated by commas in string field in QGIS

Question

In QGIS, I have a column separated by comma (shown by column "lengths"). I want to sum up elements in it for each row. The column is a text field string.

Answer 1

You can use arrays in fieldcalculator for this:

array_sum(array_foreach(string_to_array("lengths",','),to_real(@element)))

1. Turn the string into an array
2. Iterate over the array and convert the string elements to an integer or double
3. Build the sum (array_sum() available since QGIS 3.18)

To catch errors on invalid "numbers", you can use try():

array_sum(array_foreach(string_to_array("lengths",','),try(to_real(@element),0)))