Multiple columns cannot be converted to a scalar value (with format function)

[Anonymous]

Hi,

I have a table (A) with titles of books and their reading time as duration.
I have a second table (B) with reading times as provided by the publisher.
The relationship between the tables is based on table and is many to one.

Table A looks like this:
customer 1 - bookA - reading time (duration)
customer 2 - bookA - reading time (duration)
customer 3 - bookB - reading time (duration)

Table B looks like this:
bookA - expected reading time (duration)

bookB - expected reading time (duration)
bookC - expected reading time (duration)

In the Power Query editor I already transformed both of the reading time columns to duration by using this:
Tabel1 = Table.TransformColumnTypes(Tabel1_Table,{{"reading time", type time}}),
DateTimeToDuration = Table.TransformColumns(Tabel1,{{"reading time", each _ - #time(0,0,0), type duration}})

With the FORMAT function I transformed to reading time from table A to a text value and calculated the average with:

avgTime = FORMAT(

AVERAGE('reading time'[reading time]); "HH:MM:SS")

Now I also need to format the expected reading times from table B. But since those are just 1 per book title it has no use to use something like AVERAGE. Something like ALL in combination with FORMAT gives me the above in the title of this post mentioned error. 

Any ideas?
Many thanks!

[Anonymous · Accepted solution]

HI @Anonymous,

AFAIK, current power bi does not support duration type of values.
I'd like to suggest you convert it to total second and write a calculated field to transform the total second to text value with duration strings. (you can aggeration on the total second field)

Aggregating Duration Time  

Regards,
Xiaoxin Sheng

[parry2k]

@Anonymous you need to add this as a column to Format value on Table B, if you adding as a measure then use some aggregated function like MIN or MAX and then you will not get this message.