How to use private functions lib on ThingSpeak's matlab visualization like local Matlab program?

Hi all,

I would like to save my several functions once and use them in all my visualizations (as we would do it in every local Matlab program). However, I didn't find any way to do this on Thingspeak. My workaround is to copy+paste all my functions and parameters in every visualization code. This works, but it is not nice.

For example:

main program (source m-file):

% Simple test model to check compatiblity with ThingSpeak

I=[0 0 1 1 5 5 2 2 1 1]; % Assume this random signal simulates the cell current (input) in 10 seconds

for i=1:10

x=I(i);

V_ECM(i)=test_func(x,i); % solve the cell model ODE

end

plot(V_ECM) % plot to see if the model is executed correctly

function program (function m-file):

function y=test_func(x,i)

syms Vc(t)

ode=diff(Vc)+2*Vc==2*x; % Assume this is one diff equation in cell model

cond=Vc(0)==0; % assign initial conditions

Vcsol(t)=dsolve(ode,cond); % solve ODE with the given initial condition

y=Vcsol(i); % sent back calculation at current time stamp i to the main M-file

end

If I want to execute this example in one file on ThingSpeak visualization, it shows following error:

Program:

I=[0 0 1 1 5 5 2 2 1 1]; % Assume this random signal simulates the cell current (input) in 10 seconds

% Simple test model to check compatiblity with ThingSpeak

for i=1:10
    x=I(i);
    V_ECM(i)=test_func(x,i); % solve the cell model ODE
end

plot(V_ECM) % plot to see if the model is executed correctly

function y=test_func(x,i)

syms Vc(t)
ode=diff(Vc)+2*Vc==2*x; % Assume this is one diff equation in cell model
cond=Vc(0)==0; % assign initial conditions
Vcsol(t)=dsolve(ode,cond); % solve ODE with the given initial condition
y=Vcsol(i); % sent back calculation at current time stamp i to the main M-file

end

Error:

syms requires Symbolic Math Toolbox.

Error in Test>test_func (line 14)

syms Vc(t)

Error in Test (line 7)

V_ECM(i)=test_func(x,i); % solve the cell model ODE

Could anyone help on how can I call functions several time on ThingSpeak visualization like we do in Desktop Matlab program?

Thanks!

Answer 1

[Sachin Lodhi]

Hi Tanusree,

I understand that you are encountering an error while using syms on ThingSpeak's MATLAB Visualization. As a workaround for this, you can use the 'matlabFunction' to convert symbolic expression to a function handle and then you can use the function handle without Symbolic Math Toolbox.

Here is how you can achieve this -

syms test_func(x, i)
syms Vc(t)
ode=diff(Vc)+2*Vc==2*x; % Assume this is one diff equation in cell model
cond=Vc(0)==0; % assign initial conditions
Vcsol(t)=dsolve(ode,cond);
tF(x,i) = Vcsol(i);
ht = matlabFunction(tF)

ht = function_handle with value:
    @(x,i)x-x.*exp(i.*-2.0)

Now you can update the 'test_func' according to the handle 'ht' generated as shown below, to run it on ThingSpeak.

I=[0 0 1 1 5 5 2 2 1 1]; % Assume this random signal simulates the cell current (input) in 10 seconds

% Simple test model to check compatiblity with ThingSpeak

for i=1:10
    x=I(i);
    V_ECM(i)=test_func(x,i); % solve the cell model ODE
end

plot(V_ECM) % plot to see if the model is executed correctly

function y = test_func(x,i)
    y = x-x.*exp(i.*-2.0); % update according to the function handle
end

I recommend you to please go through the following documentation for more information on 'matlabFunction' : https://www.mathworks.com/help/symbolic/sym.matlabfunction.html

I hope this helps!