Obsidian | Level 7

Inverse tranformation

How do you write a code for inverse transformation in SAS??

1 ACCEPTED SOLUTION

Accepted Solutions
SAS Super FREQ

Re: Inverse tranformation

Ahh, I understand now.

If you know PROC SQL, use that to compute the max and the new (inverse transformed) variable in one step. Otherwise, you will need to compute the max (or min) in one step, put it in a macro variable, and then use the DATA step to create the new variable.

4 REPLIES 4
SAS Super FREQ

Re: Inverse tranformation

The inverse transformation of what?

If your transformation is LOG, the inverse transformation is EXP.

If your transformation is SQRT, the inverse transformation is x^2.

If your transformation is LOGISTIC, the inverse transformation is LOGIT.

In many regression procedures, you can specify ILINK on a statement to get parameter estimates on the original scale instead of the transformed scale.

Obsidian | Level 7

Re: Inverse tranformation

I think I meant to ask this:

I know we obtain inverse transformed values by using following formula.

new variable = 1/(K − old variable) (for negatively skewed data)

or 1/(C + old variable) (for positively skewed data)

K = largest score + 1
If zero is in the range use this equation, where C = smallest score + 1.

I wondered if there is SAS code that I can simply use instead of figuring out the largest or smallest values and using the formula.

But thanks for your information though.

SAS Super FREQ

Re: Inverse tranformation

Ahh, I understand now.

If you know PROC SQL, use that to compute the max and the new (inverse transformed) variable in one step. Otherwise, you will need to compute the max (or min) in one step, put it in a macro variable, and then use the DATA step to create the new variable.

Obsidian | Level 7

Re: Inverse tranformation

I don't know proc sql, so maybe I will just do the way I described.

Thanks for confirming that there isn't one code for inverse transformation!

Discussion stats
• 4 replies
• 2814 views
• 0 likes
• 2 in conversation