Thank you Johan but your proposal won't work as it is because (i) the
variables Ca, Cb, Va, Ka, Kb and Kw have not been specified (trivial to
fix), (ii) VbCalc has not been specified and I am not sure what you
intend it to be and (iii) even if I specify a value for VbCalc the line
WHILE needs to be DO WHiLE and when it is corrected to DO WHILE
generates a Data Type Mismatch error.
Clear
Ca = 0.1
Cb = 0.1
Vb = 10
Va = 10
Ka = 10^-4.757
? Ka
Kb = 10^-0.2
? Kb
Kw = 1.0E-14
HLow = 0
HHigh=10000
H=(HHigh + HLow) / 2
VbCalc = 10
DO WHILE Abs(VbCalc = Vb - Va*[(Ca/(1 + H/Ka) - H + Kw/H)/(Cb/(1 + Kw/
(H*Kb)) + H - Kw/H)]) > 0.0005
IF VbCalc < Vb
HLow=H
ELSE
HHigh=H
ENDIF
H=(HHigh + HLow) / 2
ENDDO
? H
Paul
On 20/12/2022 07:18, Johan Nel wrote:
You can do it with binaray intersect.
Vb = 10
HLow:= 0
HHigh=10000
H=(HHigh + HLow) / 2
WHILE Abs(VbCalc = Vb - Va*[(Ca/(1 + H/Ka) - H + Kw/H)/(Cb/(1 + Kw⁄
(H*Kb)) + H - Kw/H)]) > 0.0005
IF VbCalc < Vb
HLow=H
ELSE
HHigh=H
ENDIF
H=(HHigh + HLow) / 2
ENDDO
HTH
Johan Nel
South Africa
On 2022/12/14 01:49, Paul Newton wrote:
I have the following equation
Vb = Va*[(Ca/(1 + H/Ka) - H + Kw/H)/(Cb/(1 + Kw⁄ (H*Kb)) + H - Kw/H)]
Va, Ca, Ka, Cb, Kb and Kw are known or can be provided for any given
"run" of the calculation. Typical values might be
Va = 10, Ca = 0.1, Ka = 1.8E-5, Cb = 0.1, Kb = 0.63, Kw = 1.0E-14
The aim is to calculate H for various values of Vb and this requires
"solving" for H. Various software packages do this in pretty much the
same way but the terminology varies: Matlab uses "fsolve", Mathcad
uses "find", Maple uses "solve" and Excel uses "GoalSeek".
I would like to try to find a way of doing this from VFP. Perhaps
there is already a .NET DLL that could be called from VFP? Perhaps
with a wrapper to act as a sort of mediator? Failing that, would it
be a major task to create something in .NET (perhaps using an
existing package)?
I really don't know, just thinking aloud ...
Paul Newton
[excessive quoting removed by server]
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