15 replies to this topic

[Joseph Bove]

Gang,

This is a new requirement for me. I need to be able to run calculations that include logarithms within ProIV. I can't seem to locate a log(#n) logic command. Has anyone been down this road?

Thanks,

Joseph

[Tyleulen]

I sure hope there is a better answer than this one...

http://www.vb-helper...o_make_dll.html

[Joseph Bove]

Tyleulen,

That would just be sad...

Thanks,

Joseph

[Rick Young]

Even sadder, or perhaps simply worse - depending on a) how precise you wished to be and how much process-time you have.....

FOR #I = 2 TO 1000
IF REM(#I,2) = 0 THEN
#L = #L - ((#X ** #I) / #I)
ELSE
#L = #L + ((#X ** #I) / #I)
ENDIF
ENDFOR


Where #X = number to derive logarithm of, less 1.

Edit: and #X is sufficiently small ....

Edited by Rick Young, 06 July 2006 - 08:52 PM.

[Joseph Bove]

Rick,

Thanks for the post. It at least gave me a chuckle and was slightly better than my fall back position...

#X = 42

Regards,

Joseph

[Neil Hunter]

Nevermind...

Edited by Neil Hunter, 07 July 2006 - 05:04 AM.

[Joseph Bove]

Old fart,

Ok, I have to ask, what do your friends call you?

Anyhow... I like the SQL idea. Does SQL have a logarithm tool built into it? I guess I can just google to try find as such.

Thanks for the idea.

Regards,

Joseph

[Joseph Bove]

Guest,

No, I don't have to worry about porting it.

I do have to worry about it working on SQL Server, Oracle and Postgresql...

Regards,

Joseph

[Neil Hunter]

Sorry, that was me.

You come right or must I do some more digging ?

[Joseph Bove]

Rick,

I finally got around to trying the code below:

FOR #I = 2 TO 1000
IF REM(#I,2) = 0 THEN
#L = #L - ((#X ** #I) / #I)
ELSE
#L = #L + ((#X ** #I) / #I)
ENDIF
ENDFOR

ProIV cannot handle exponents > 128. When I cut the loop to 100, I don't appear to be getting "good" values.

Do you have any other ideas?

Regards

Joseph

[Joseph Bove]

Gang,

An ok solution for logs... it works.

For my specific scenario, I knew that the log would be from numbers within the range of .00000001 and 100.

#MIN = -8
#MAX = 2
#TRY = -3
PRECISION(12)
FOR #PRECISION = 1 TO 200
  #TEN_TO_THE_X = 10 ** #TRY
  IF (#TEN_TO_THE_X < #VALUE_TWO) THEN
    #NEW_MIN = #TRY
    #TRY += ((#TRY - #MIN) / 2)
    #MIN = #NEW_MIN;
  IF (#TEN_TO_THE_X > #VALUE_TWO) THEN
    #NEW_MAX = #TRY
    #TRY -= ((#MAX - #TRY) / 2)
    #MAX = #NEW_MAX;
  IF (#TEN_TO_THE_X = #VALUE_TWO) THEN LOOPEXIT;
ENDFOR
#VALUE = #TRY

May you never have to code this yourself...

Regards,

Joseph

[Rick Young]

Sorry Joseph - hellish day yesterday, and unfortunately no ideas for you.

Nice job