@Mark_Bailey : Sure, there is no difference at all between N row(dt) and the non-existing dt << n rows
... from the point of view of what you get.
But this post is about idioms of the jmp language which can make it hard for newbies to get what they want.
Sometimes, there are tiny "walls" or you get stuck in front of a locked door - this can be frustrating or irritating.
I could imagine that during the Trial Period some potential users of JMP got lost to other languages like Python or Matlab because of such difficulties.
The benefit of messages:
Let's imagine that a user has a data table dt and knows already that he can send messages like << get name to the object.
He also knows that typing
dt << get
and pressing CTRL+Space will help him to get possible candidates for what he wants.
And indeed, there is a << get rows() for data tables.
Unfortunately, this function does something else
Therefore, he keeps searching and searches the Scripting Index for other messages like Nitems, Length, Dimensions and so on.
Nothing - along the idea: If you don't know the correct function name, I cannot give you the correct info.
Then he just selects the data table object and scans all these messages, which can be sent to a data table. A huge list, but none of them does what the user wants. This takes a while ...
Another user uses the Scripting index and tries
then:
and scans the first 10 entries. Hm ...
(compare: https://www.google.com/search?q=length+data%20table+python)
As a next step, both go to the JMP Community:
https://community.jmp.com/t5/forums/searchpage/tab/message?q=data%20table%20number%20rows
and find out that they were not the only ones who had this problem - what a relief!
And that's not all.
Fortunately, there are people who passionately help other users with their problems
From now on, both can tell other people that the function is not "length()", "dimensions()", "len()", "size()" .... , but N row().
And that dt << N Rows() is not available because it would just be the same as N row(dt)
... or N Rows(dt).