Default null values in transpose

Hi,

I'm trying to do a transpose on some data that has a lot of empty cells (counts of errors by host), and to make the graph look correct, I need to default empty cells to 0 (otherwise they just get extrapolated from the previous non-null value, so there appears to be data where there is not).

The 'transpose' docs say to use isNull for this, and the isNull docs say that it can be used to supply defaults for transpose, but neither one actually gives an example, and I can't figure it out.

My query is something like this: "failed" | timeslice 10m | count by _timeslice, syslog_host | transpose row _timeslice column syslog_host

I tried adding something like "| if (isNull(_count), 0, _count) as _count", but it says _count is not defined.

Anyone know? Thanks.