topic Re: Convert array into string in Discussions

Convert array into string

29755 — Sat, 10 Jun 2023 23:33:59 GMT

Hi all,

I am trying to get a value from an array from another table and use it as value for my selection. Is there a way to get convert the array into a string?

name_key = associative array(column(ref_file_1, "NAME") << get values) << get keys;
merged_file << select where(:Name_final==name_key);

Re: Convert array into string

txnelson — Fri, 16 Jul 2021 03:29:07 GMT

I think this will give you what you want

name_key = associative array(column(ref_file_1, "NAME") << get values) << get keys;
merged_file << select where(nrows(loc(name_key,:Name_final))>0);

Re: Convert array into string

Craige_Hales — Fri, 16 Jul 2021 10:42:19 GMT

Again, amazed at Jim's ability to get to the heart of the question. Two nice bits of code here deserve a longer explanation:

What does this do?

name_key = associative array(column(ref_file_1, "NAME") << get values) << get keys;

ref_file_1 is a data table reference, "NAME" is a column's name as a string (literally, "NAME", but could be in a variable), and the column function returns a column reference. The <<get values message gets all the values from the column, including duplicates. The associative array function creates a set of the unique values, and the <<get keys message returns the unique values. (Nicely done @29755.)

and this?

merged_file << select where(nrows(loc(name_key,:Name_final))>0);

The <<select where message operates on each row of the merged_file, one at a time and selects rows when the argument is non-zero.

The loc() function returns a matrix of indexes. It searches the list in name_key for occurrences of :Name_final. The resulting matrix can have zero or more rows, though in this example it will have 0 or 1 row because the keys are unique. The nrows() function returns 0 or 1 which is then compared >0 and remains 0 or 1. So rows are selected if :Name_final is in the list of ref_file_1:NAME.

Alternative:

What if there were >1e6 names in name_key and >1e7 rows in merge_file? What would the performance look like? The loc function will be searching, a lot. It will compare 1e13 strings. You'll get tired of waiting. The fix for that is to use the associative array like this:

nameSet = associative array(column(ref_file_1, "NAME") << get values);
merged_file << select where(contains(nameSet, :Name_final));

Now there are only 1e7 lookups in nameSet. They are not free, but they are much faster than checking 1e6 items sequentially. I'll guess about 20 compares each (log2(1e6)). This may also be easier for the next maintainer to follow.

(Untested. Corrections welcome!)

Re: Convert array into string

txnelson — Fri, 16 Jul 2021 12:44:22 GMT

Craige,

Once again I learned something new about JMP. I had originally written the code using a Contains() function, but then converted to using the Loc() function, because what I thought would be an issue where

Contains( "BARBARA ANN", "BARBARA")

returns a True.

I had (wrongly it turns out) that if the compare component of the Contains is a JMP List of items,

Contains( {"BARBARA ANN", "BETTY", "DAVID"}, "BARBARA")

would also return a True, however, it returns a False, which means it does an absolute match.

Thanks for the great info