topic Re: How does SUBSTR= work with leading blanks in SAS Programming

How does SUBSTR= work with leading blanks

mftuchman — Thu, 18 Jul 2019 18:45:30 GMT

What would you expect the output of this code to be? What about the value of x in the 'v2' put statement?

data _null_;
length x $200;
x='?';
substr(x,70,1)='!';
put 'v1' x= $char200.;
x=' ';
substr(x,60,8)='la chose';
put 'v2' x= $char200.;
run;

For the second one, I expected 59 blanks followed by the text. This expectation was apparently in error. How could I have predicted the observed behavior (X='la chose' with no leading blanks)?

Please don't ask me what I'm trying to do. I already solved that; now I'm just curious as to how SUBSTR= works with blanks. The SUBSTR (left side of 😃 page of the SAS documentation did not specify this behavior.

Re: How does SUBSTR= work with leading blanks

data_null__ — Thu, 18 Jul 2019 18:55:23 GMT

@mftuchman wrote:

What would you expect the output of this code to be? What about the value of x in the 'v2' put statement?
data _null_;
length x $200;
x='?';
substr(x,70,1)='!';
put 'v1' x= $char200.;
x=' ';
substr(x,60,8)='la chose';
put 'v2' x= $char200.;
run;
For the second one, I expected 59 blanks followed by the text. This expectation was apparently in error. How could I have predicted the observed behavior (X='la chose' with no leading blanks)?

Please don't ask me what I'm trying to do. I already solved that; now I'm just curious as to how SUBSTR= works with blanks. The SUBSTR (left side of 😃 page of the SAS documentation did not specify this behavior.

X= in the PUT statement specifies NAMED-PUT leading/trailing blanks are trimmed.

data _null_;
   length x $200;
   x='?';
   substr(x,70,1)='!';
   put 'v1' x $char200.;
   x=' ';
   substr(x,60,8)='la chose';
   put 'v2' x $char200.;
   run;

Re: How does SUBSTR= work with leading blanks

mftuchman — Thu, 18 Jul 2019 21:12:15 GMT

[to be deleted]

Re: How does SUBSTR= work with leading blanks

ballardw — Thu, 18 Jul 2019 19:41:52 GMT

Consider

data junk;
length x $200;
x='?';
substr(x,70,1)='!';
put 'v1' x= $char200.;
x=' ';
substr(x,60,8)='la chose';
l = length(x);

run;

If you open the data set junk with any of the SAS viewers you will see a bunch of leading spaces. The value of L will count the leading spaces plus the actual text ending at the 'e' in 'chose'.

Re: How does SUBSTR= work with leading blanks

Tom — Thu, 18 Jul 2019 20:01:26 GMT

Given that you seem to know what you are doing I am not sure I follow what the question is.

SAS stores all character variables as fixed lengths strings that are padded with spaces. So if you start with a missing/null/empty variable of length 200 it has 200 spaces in it. If you then change 70th position into an X it now has 69 spaces one X and then 130 spaces.

Re: How does SUBSTR= work with leading blanks

Astounding — Thu, 18 Jul 2019 20:03:50 GMT

SUBSTR= does not replace X. Instead, it replaces some of the characters in X (in this case, characters 60 through 67), leaving any other characters in X unchanged.

Re: How does SUBSTR= work with leading blanks

mftuchman — Thu, 18 Jul 2019 21:18:09 GMT

The question was originally "why do my leading spaces disappear?". Is it possible that SUBSTR= does not do what I think it does? But it does; it was the named PUT that threw me off. When I surrounded it with delimiters, the spaces were visible.

And I have to remember that single quote works for SAS, but not for English grammar 🙂

Re: How does SUBSTR= work with leading blanks

mftuchman — Thu, 18 Jul 2019 21:15:40 GMT

Not trying to replace X - just trying to visualize a sparse vector in plain text, so I want to build a long blank string and then populate segments of it using substr=.

Turns out I got an easier to read result by using a non-destructive function CATX(OF ....) to build my string.

Hope that background helps a litt.e