Log function within loops

[Mahmoud Amoli]

Hello Stata experts,

I am trying to perform a log function within loops, but it gives me errors that I do not know how to fix it. Your help would be much appreciated. Thanks!

This is the code that I am running:

forvalues i = 6/40 {
    forvalues j = 1/6{
        foreach k in lmn if gestage2==`i' & bmiprepregcat6==`j'{
            foreach l in lsd if gestage2==`i' & bmiprepregcat6==`j'{
                replace zscore = (log(gwgkg +`c')-`k')/`l' if gestage2==`i' & bmiprepregcat6==1
            }
        }
    }
}

This code gives me the r(198) error, but I already created the "gwgkg" as a continuous variable and I do not know why the plus (+) sign got mixed up with the variable name.

gwgkg+ invalid name
r(198);

I tried using parenthesis to make the variable name "gwgkg" and it does not work either.

forvalues i = 6/40 {
    forvalues j = 1/6{
        foreach k in lmn if gestage2==`i' & bmiprepregcat6==`j'{
            foreach l in lsd if gestage2==`i' & bmiprepregcat6==`j'{
                replace zscore = ((log(gwgkg) +`c')-`k')/`l' if gestage2==`i' & bmiprepregcat6==1
            }
        }
    }
}

Now the error is:

unknown function ()
r(133);

Thank you!

[Nick Cox]

The local macro c is not defined.

Putting an if qualifier on a loop makes no sense to Stata but that has yet to crash your code.

[Mahmoud Amoli]

Thanks for your response dear Nick Cox,

I defined the local c in the data, but I forgot to put it here:

local c = 5.55

The original code that I created the loop for looks like this:

replace zscore=(log(gwgkg+`c')-1.870)/0.337 if gestage2==6 & bmiprepregcat6==1
replace zscore=(log(gwgkg+`c')-1.896)/0.330 if gestage2==7 & bmiprepregcat6==1

the numbers 1.87 and 1.896 are coming from the "lmn" variable and 0.33 and 0.337 are from the "lsd" variable"

thanks!

[Nick Cox]

The issue is not what you forgot; it's that Stata can't see the definition.

Why isn't this just

replace zscore = ((log(gwgkg) + 5.55)- lmn)/lsd

This looks legal

  
 forvalues i = 6/40 {     forvalues j = 1/6 {         replace zscore = ((log(gwgkg) + 5.55)-lmn)/lsd if gestage2==`i' & bmiprepregcat6==`j'      } }

[Mahmoud Amoli]

The reason that I had to define a local instead of simply putting 5.55 is I have multiple values for c such as 5.55 - 9- 12- 18.

Thank you!

[Nick Cox]

I think there is no way that was clear in anything you've said so far. But if c is variable your code needs to adjust to that.

If you can't work out which way to go now, we need a heap more context about what the goal is.

[Mahmoud Amoli]

Dear Nick Cox,

I see! That's ok; I can do the rest manually, not a big deal.

Thank you so very much; You are great,!

and btw, I am a great fan of your tutorials