Cannot convert the value null to type Logical

[Naomig2088]

I have a conditional column:

if [startdate] >= [validtodate] then 1 else 0

which produces a result. However when I filter on the result column (only to include 1) and then group the result, I'm presented with the above error.

Can anyone please offer a solution?

Many thanks.

[HotChilli · Accepted solution]

Ok, so this is all in Power Query preview screen?

What is the Grouping M code? 

Do you have null values in your data?

[Naomig2088]

I've just realised I had null value in one column. There was so much data that it hadn't all loaded so I didn't see it intially, but once I've selected 'load more' it's become visible.

Thank you for your help!

[HotChilli]

"when I filter on the result column" - you have created a visual with the column in it? What visual and what else is in it?

"then group the result" - what does this mean? how are you grouping it?

[Naomig2088]

Sorry, no, when I say filter, I mean, once I have the result of the conditional column above then I've filtered that column to only show the '1'.