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How to convert a numeric list into a character one?

anne_sa

Hi everybody,

I have a list containing numbers and I would like to transform them into characters. Is there a way to do that without using a loop? I was not able to find the proper function.

Thanks for your help!

Accepted answers

Jeff_Perkinson

New in JMP 16 is the For Each() function which iterates over a container – list, matrix, or associative array – to perform an operation on each element.

Here is an example to show how to use it to convert your list of numbers to a list of character strings.

Names Default To Here( 1 );
theList = {7, 8, 9};

For Each( {value, index}, theList, theList[index] = Char( value ) );

All comments

txnelson

Here is a little script that creates a function that does what you want. You can either define and use the function in your code, or use the 4 statements in open code to do the conversion.

Names Default To Here( 1 );
theList = {7,8,9};

NumListToChar = Function( {myList},
	{defaultlocal},
	dtx = New Table( "x", New Column( "y", values( myList ) ), private );
	dtx:y << data type( character );
	myList = dtx:y << get values;
	Close( dtx, nosave );
	Return( myList );
);

theList = NumListToChar( theList );

anne_sa

Thanks for your answer @txnelson it is indeed what I was looking for.

I just wonder what is the faster between a loop and a function which involves table creation. Any idea?

Jeff_Perkinson

New in JMP 16 is the For Each() function which iterates over a container – list, matrix, or associative array – to perform an operation on each element.

Here is an example to show how to use it to convert your list of numbers to a list of character strings.

Names Default To Here( 1 );
theList = {7, 8, 9};

For Each( {value, index}, theList, theList[index] = Char( value ) );

anne_sa

Thanks @Jeff_Perkinson !

I did some simulations just by curiosity to compare the execution time of each solution and it seems that the for each function is on average the fastest one!

So I am gonna pick that one although the function of @txnelson also works very well.

Thanks to both of you

Jeff_Perkinson

Here's a quick timing program for the three methods, for loop, for each, and custom function using data table.

Names Default To Here( 1 );

listsize=1000000;

theList = As List( J( listsize, 1, Random Integer( 100 ) ) );

NumListToChar = Function( {myList},
	{defaultlocal},
	dtx = New Table( "x", New Column( "y", values( myList ) ), private );
	dtx:y << data type( character );
	myList = dtx:y << get values;
	Close( dtx, nosave );
	Return( myList );
);

start = HP Time();
For Each( {value, index}, theList, theList[index] = Char( value ) );
foreachloop = HP Time() - start;

theList = As List( J( listsize, 1, Random Integer( 100 ) ) );

start = HP Time();
theList = NumListToChar( theList );
customfunction = HP Time() - start;

theList = As List( J( listsize, 1, Random Integer( 100 ) ) );

start = HP Time();
For( i = 1, i <= N Items( theList ), i++,
	theList[i] = Char( theList[i] )
);
forloop = HP Time() - start;

show(foreachloop, customfunction, forloop);

For me with the listsize shown above the results are very similar between the three methods:

foreachloop = 1106974;
customfunction = 1077862;
forloop = 1400643;

XanGregg

There's also Transform Each, which appears to be a little faster than For Each here.

	theList = Transform Each( {value}, theList, Char( value ) );