Extracting the first non-zero digit from a numeric variable

[tritringuyen]

Hi all,

I have a problem with my dataset. From given variables (numberic), I want the first non-zero digit of positive numbers, negative numbers and decimals. Unfortunately, a variable may have any of those numbers. I may have million numbers in my datasets (more than 150 variables * more than 10,000 rows). Please find the attachment for example of wanted variable.

Thank you very much for your help. Please explain your coding when possible. Thanks!

Best Regards,

Tri

[ballardw]

What is the desired result if the value is exactly 0?

Here's one way, without implementing a result for 0;

data want;
   input x;
   y = substr(strip(compress(put(x,best32.),'0-.')),1,1);
datalines;
0.1
-0.008
1234
-456.98
;
run;

[tritringuyen]

Thanks for your support!

[Elle · Accepted solution]

data have;
	input numvar;
	datalines;
89
-56
0.89
0.007
-0.008
;run;

data want;
	set have;
	wantvar=substr(compress(numvar, "+-0., "), 1, 1)*1;
run;

        /* COMPRESS function eliminates all characters in quotes from your variable */
	/* SUBSTR function extracts characters from a position of 1, of a length of 1 */
	/* Since SUBSTR is a character function it turn the variable into character, so to make it numeric again I just multiply by 1 */ 

[tritringuyen]

Thank you very much for your response and explanation! I found that your code works for me. Many thanks! Tri

[PGStats]

Mathematically,

if x = 0 then firstDigit = 0;

else firstDigit = floor(10**(log10(abs(x)) - floor(log10(abs(x)))));

beyond mathematical concepts, coding is explained in the SAS documentation of log10, floor and abs functions.

data test;
do x = -123545, -2.34, -0.34567, 0, 0.00004567, 0.5678, 6.789, 789.012, 8.901e12;
    if x = 0 then firstDigit = 0;
    else firstDigit = floor(10**(log10(abs(x)) - floor(log10(abs(x)))));
    output;
    end;
format x e10.;
run;

proc print; run;

[Haikuo]

Or PRX:

data have;
	input var1;
	cards;
89467
-5678944
0.89776
0.000677755
-0.0023456
;
run;

data want;
	set have;
	var_c=put(var1,best.);
	first_d = prxchange('s/([^1-9]*)([1-9])(.*)/$2/io',-1,var_c);
run;

[Ksharp]

data want;
   input x;
   temp=put(x,best32.);
   y = substr(temp,prxmatch('/[1-9]/',temp),1);
   drop temp;
datalines;
0.1
-0.008
1234
-456.98
;
run;