Seek help on Create new var with Do Loop

[Minhtrang]

I want to create new variables (newna1-newna5) from na1 -na5, if there is missing value of na then 
newna will be equal to the previous nonmissing value of na.
But I have problems running the program below, error with array length.
Please help me to figure it out.
Thank you very much

data try;
	input id na1 na2 na3 na4 na5;
	datalines;
1 2 3 . . 4 
2 3 5 4 1 .
3 6 . 7 5 4
4 5 3 . 4 .
5 4 . . . 6
;
run;

data try1;
	set try;
	array na(*) na1-na5;
	array newna(*) newna1-newna5;

	do i=1 to 5;
	newna(i)=na(i);
                do j=1 to 4;
		if na(i)=. then newna(i)=na(i-j);
		end;
		
	end;
run;

		output;

[Astounding · Accepted solution]

You could simplify the process and get the correct result most of the time:

data try1;
	set try;
	array na(*) na1-na5;
	array newna(*) newna1-newna5;

	do i=1 to 5;
	   if na(i) > . then newna(i)=na(i);
	   else newna(i)=newna(i-1);
	end;
run;

When I say "most of the time" I'm looking at the possibility that na1 might be missing.  What should happen in that case?  The program will generate an error as it stands now.  So if it's possible that na1 might be missing, you would need to specify what the result should be so the program can be modified.

[Minhtrang]

Dear Astouding,

Thanks a lot for your help.

It's so simple!

Best,

Trang