New Function VBA / Beginner

[Cocotte]

I need to create a VBA Function in order to calculate the Antoine Formula.
P = 10^(A-(B/T+C))
T= Degree Celsius P= mmHg
Example: http://ddbonline.ddbst.com/AntoineCalculation/AntoineCalculationCGI.exe?component=Methanol
I got to say the Celsius is making me totally confuse.
<code style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-variant: inherit; font-weight: inherit; font-stretch: inherit; line-height: inherit; font-family: Consolas, Menlo, Monaco, "Lucida Console", "Liberation Mono", "DejaVu Sans Mono", "Bitstream Vera Sans Mono", "Courier New", monospace, sans-serif; vertical-align: baseline; box-sizing: inherit; white-space: inherit;">Function antoine( A as double, B as Double, C as Double, T as Double) aS Double
Dim T as ..........
antoine= 10^(A-(B/T+C))
End Function</code>Thanks

 

[Scott Huish]

I don't understand the topic in your link but you don't want to redim values that you are using as parameters in your function and you do need a space between the as and the data type. Your parentheses didn't seem quite correct though.

Function antoine(A As Double, B As Double, C As Double, T As Double) As Double
antoine = 10 ^ (A - (B / (C + T)))
End Function

Excel 2010
	A	B	C	D	E
1	8.08097	1582.27	239.7	100	2649.262
Sheet1

Cell Formulas
Range	Formula
E1	=antoine(A1,B1,C1,D1)

 

[Rick Rothstein]

[COLOR=[URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=2]#2[/URL] 42729]I got to say the Celsius is making me totally confuse.
[/COLOR]

Is your problem that you have your temperatures in degrees Fahrenheit? If so, try this for your function...

[table="width: 500"]
[tr]
	[td]Function Antoine(A As Double, B As Double, C As Double, T As Double) As Double
  Antoine = 10 ^ (A - (B / (C + 5 * (T - 32) / 9)))
End Function[/td]
[/tr]
[/table]

Note: I applied the correction for your parentheses as Scott pointed out in Message #2 .

 

[Cocotte]

Is your problem that you have your temperatures in degrees Fahrenheit? If so, try this for your function...

[TABLE="width: 500"]
<tbody>[TR]
[TD]Function Antoine(A As Double, B As Double, C As Double, T As Double) As Double
  Antoine = 10 ^ (A - (B / (C + 5 * (T - 32) / 9)))
End Function[/TD]
[/TR]
</tbody>[/TABLE]

Note: I applied the correction for your parentheses as Scott pointed out in Message #2 .

My confusion with "T" is that, how excel know this is Celsius? Don't I need to define the value differently?

Thanks for the parenthesis, I didn't realized right away.

 

[Rick Rothstein]

My confusion with "T" is that, how excel know this is Celsius? Don't I need to define the value differently?

Excel doesn't know anything... all it sees is that you are passing in a number for the T argument.... it is the formula that "knows", well, rather "assumes", that the number is Celcius. It is incumbent on you (or your workbook's user) to know that the number inputted for T is supposed to be Celsius and to make sure that is the only kind of temperature that is specified. There would be know way for the formula to determine if the number is Celsius or Fahrenheit on its own (that is because the possible ranges for each overlap each other... if you pass in 40, that would be a legitimate value in either temperature scale). If you know you will always be working in Celsius, then use the formula Scot gave you; but if instead you know your values will always be Fahrenheit, then use the code I gave you instead (it converts Fahrenheit to Celsius directly within the code).