topic Re: negative exponents in SAS/IML Software and Matrix Computations

negative exponents

Salah — Mon, 26 Apr 2021 21:42:00 GMT

Hello

I am not sure how to ask this question.

Is there a way to format the output in case of very very small numbers without rounding them

For example 0.0000006 can I have SAS to write the output as 6 e^-6 or anything similar?

I know that there is round(x,0.0001) but I want to keep the number as it is just the output to be in short hand.

Thank you

Re: negative exponents

PaigeMiller — Mon, 26 Apr 2021 21:51:27 GMT

Your question is about how to do this in PROC IML?

Where do you want to see this formatted output? Please be very detailed.

Re: negative exponents

Reeza — Mon, 26 Apr 2021 21:55:37 GMT

Formats.

Exponential formats are probably what you want...but where are you planning to use this in IML?

Not 100% sure this can be used in whatever step you're looking for it.

@Salah wrote:

Hello

I am not sure how to ask this question.

Is there a way to format the output in case of very very small numbers without rounding them

For example 0.0000006 can I have SAS to write the output as 6 e^-6 or anything similar?

I know that there is round(x,0.0001) but I want to keep the number as it is just the output to be in short hand.

Thank you

Re: negative exponents

ballardw — Mon, 26 Apr 2021 22:07:46 GMT

The format is amazingly enough the Ew. format, for exponential. For example e10. preserves 10 significant digits

data example;
   x= 0.0000002345;
   put x= e10.;
run;

with a result of

x=2.345E-07

The format can be used to display 32 characters but the documentation displays up to 14 significant digits.

Re: negative exponents

Rick_SAS — Tue, 27 Apr 2021 00:40:35 GMT


proc iml;
power = -10:-3;
x= 10**power;
print x[format=E10.];

Re: negative exponents

Ksharp — Tue, 27 Apr 2021 12:36:29 GMT

Rick,
Shouldn't be
x= 10##power;
??
** in IML is matrix multiply operator ?

proc iml;
a={1 2,
4 2};
x= a##2;
y= a**2;
print x / y;
quit;

Re: negative exponents

Rick_SAS — Tue, 27 Apr 2021 15:45:19 GMT

When the base is a scalar, the ** and ## operators are equivalent. I used 10**power since most DATA step programmers are more familiar with the ** operator for raising a scalar to a power.

But, sure, you can use ## if you prefer.

Re: negative exponents

Salah — Tue, 27 Apr 2021 19:54:11 GMT

Thank you for the help. But I am not sure this works in SAS/IML!