Array indices must be positive integers or logical values error when using cell arrays

The following code is supposed to add a function of x to a function handle f whose coefficients depend on the entries of a cell array a.

a = {{'P',8,0},{'l',-8,0,4},{'P',40,4},{'P',6,-16}}
x = linspace(0,6); 
f = @(x) 0;   
f= f(x) + a{1}{2}*x.^7 
for i = 1:numel(a)
if a{i}{1} == 'P' 
    f = f(x) + a{i}{2}*x;  
end
end

There are no problems in doing this when a polynomial is added outside the for loop but the error message is displayed because of the polynomial a{i}{2}*x which is included in the for loop.

Does anyone have suggestions on how to fix this issue?

Answer 1

[Ameer Hamza]

You are overwriting the function handle f. Change the name of variable in which you are storing the sum.

a = {{'P',8,0},{'l',-8,0,4},{'P',40,4},{'P',6,-16}}
x = linspace(0,6); 
f = @(x) 0;   
f_ = f(x) + a{1}{2}*x.^7 
for i = 1:numel(a)
if a{i}{1} == 'P' 
    f_ = f(x) + a{i}{2}*x;  
end
end

[Aleem Andrew]

Thank you for your help

[Ameer Hamza]

I am glad to be of help!