How do I generate executable code from imported data?

I have an xlsx file with various data for the calculation I'd like to conduct with my Matlab code. This file also contains the relevant formulas. Is there a way to import those formulas from xlsx (having them as a string) and convert them to normal code thats executable?

[Dyuman Joshi]

Can it be done? Yes. Is it recommended? No.

Though, you could define the formulae in the syntax of function handles and utilize str2func to convert them to anonymous functions, and use accordingly.

[Johannes]

That is a good approach, thank you. However, the str2func command does not accept variables from outside the function. As I have pre-defined variables, there is an issue with the function

[Dyuman Joshi]

Can you show what the formulas look like? It will even better if you could attach the excel file.

[Johannes]

I made a test script for the function. My minimum code example looks like this:

clear all
close all
clc


Flushmatrix = readtable('Spülmatrix2.xlsx','PreserveVariableNames',true); 
%%
psat = 1.5;
p_fmin = psat+1;
v = 330;
%%
a = Flushmatrix(1,9);
a = string(table2cell(a));
%%
fh = str2func(a)
fh(v, psat, p_fmin)

The xlsx file contains the variables and functions. I attached it to this comment. The problem is that the function is not callable like this. If I try to run it with my preset variables, it gives this error:

Undefined function
'((table2array(Flushmatrix(1,3))*(v/1000)+table2array(Flushmatrix(1,4)))*log(psat)+(table2array(Flushmatrix(1,5))*v+table2array(Flushmatrix(1,6))))/1000'
for input arguments of type 'double'.

Error in str2func_Test (line 16)
fh(v, psat, p_fmin)

[Dyuman Joshi]

Sorry, I was away from my PC due to some other work. Please check my answer below.

Answer 1

[Dyuman Joshi]

You need to add the @(list_of_independent_variables) before the formulae.

Flushmatrix = readtable('Spülmatrix2.xlsx','PreserveVariableNames',true)

Flushmatrix = 3×9 table
       Spülen       Produkt     K1 [s/mL]     K2 [s]      K3 [s/mL]     K4 [s]      K5       K6                                                                                                                                       Funktion                                                                                                                                   
    ____________    ________    _________    _________    _________    ________    _____    ____    _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

    {'standard'}    {'Bier'}    -0.23643     -0.040387      0.7205     0.039548      NaN     NaN    {'@(Flushmatrix, v, psat) ((table2array(Flushmatrix(1,3))*(v/1000)+table2array(Flushmatrix(1,4)))*log(psat)+(table2array(Flushmatrix(1,5))*v+table2array(Flushmatrix(1,6))))/1000''                                                                                         }
    {'standard'}    {'CSD' }    -0.17236     -0.038639     0.47643     0.037187      NaN     NaN    {'@(Flushmatrix, v, psat) ((table2array(Flushmatrix(2,3))*(v/1000)+table2array(Flushmatrix(2,4)))*log(psat)+(table2array(Flushmatrix(2,5))*v+table2array(Flushmatrix(2,6))))/1000''                                                                                         }
    {'sanft'   }    {'Bier'}       175.4         -1666      -345.6         3823    3.032    -305    {'@(Flushmatrix, v, psat, p_fmin) ((table2array(Flushmatrix(3,3))*p_fmin+table2array(Flushmatrix(3,4)))*(v/1000)^2+(table2array(Flushmatrix(3,5))*p_fmin+table2array(Flushmatrix(3,6)))*(v/1000)+(table2array(Flushmatrix(3,7))*p_fmin+table2array(Flushmatrix(3,8))))/1000'}

%values for variables
psat = 1.5;
p_fmin = psat+1;
v = 330;

%Value from the formula copied and pasted
((table2array(Flushmatrix(1,3))*(v/1000)+table2array(Flushmatrix(1,4)))*log(psat)+(table2array(Flushmatrix(1,5))*v+table2array(Flushmatrix(1,6))))/1000

ans = 0.2378

%formula from the table read
a = Flushmatrix(1,9);
a = string(table2cell(a))

a = "@(Flushmatrix, v, psat) ((table2array(Flushmatrix(1,3))*(v/1000)+table2array(Flushmatrix(1,4)))*log(psat)+(table2array(Flushmatrix(1,5))*v+table2array(Flushmatrix(1,6))))/1000'"

%convert the string to a function handle
fh = str2func(a)

fh = function_handle with value:
    @(Flushmatrix,v,psat)((table2array(Flushmatrix(1,3))*(v/1000)+table2array(Flushmatrix(1,4)))*log(psat)+(table2array(Flushmatrix(1,5))*v+table2array(Flushmatrix(1,6))))/1000'

%corresponding value
fh(Flushmatrix, v, psat)

ans = 0.2378

[Dyuman Joshi]

Though, I am wondering, can't you just copy and paste the formulas from the excel file to MATLAB?

[Johannes]

Thank you so much for the help. We are working with the Matlab App Designer, so in the long term this could maybe be implemented in an app. There might be users with no Matlab license, so it`s more convenient to just change the xlsx file when one needs to change the formulae or coefficients.

[Dyuman Joshi]

I see.

Also, you can modify this lines -

a = Flushmatrix(1,9);
a = string(table2cell(a));
fh = str2func(a);

to

fh = str2func(Flushmatrix{1,9})

For more info - Access Data in Tables