How do I define a variable from another function? - matlab

Question

I have a multi-fuction script that is supposed to ask the user for 4 different cars and weigh them based on ratings to give the user the best car to purchase.
What I want to do is have a prompt for every car the user inputs so the user can put in data for each variable the user decides to use. However, when titling the prompt I want to use the cars name in the prompt. It seems impossible to me and Im not sure what to do, im very new to coding.
Main Script
prompt1 = {'How Many Cars (4): '};
title1 = 'Cars';
answer1 = inputdlg(prompt1, title1, [1 40]);
Q1 = str2double(answer1{1});
[N] = Group_Function1(Q1);
Car1 = N(1); %Stores the names of the cars
Car2 = N(2);
Car3 = N(3);
Car4 = N(4);
prompt2 = {'How Many Variables (4): '};
title2 = 'Variables';
answer2 = inputdlg(prompt2, title2, [1 50]);
fprintf('This code can accept costs between 0-100000\n');
fprintf('This code can accept top speeds between 0-200\n');
fprintf('This code can also accept the terms none, some, & alot\n');
fprintf('This code can accept safety ratings between 0-5\n');
Q2 = str2double(answer2{1});
[V,W] = Group_Function2(Q2);
W1 = W(1); %Stores the weights of the varibles
W2 = W(2);
W3 = W(3);
W4 = W(4);
for h=1:Q1
[H] = Group_Function3(V);
Weights(h,:)=H;
end
Group_Function1
function [N] = Group_Function1(Q1)
for Q = 1:Q1
prompt = {'Name of Car:'};
title = 'Car Name';
answer = inputdlg(prompt,title, [1 80])';
N(Q) = answer(1);
end
Group_Function2
function [V,W] = Group_Function2(Q2)
for Q=1:Q2
prompt = {'Variable? (Negative Variables First):','weights in decimal
form?'};
title = 'Variables and Weights';
answer = inputdlg(prompt,title, [1 80])';
V(Q)=answer(1);
W(Q)=str2double(answer{2});
s=sum(W);
end
if s~=1
fprintf('Weights do not add up to 1. Try Again!\n');
Group_Function2(Q2);
end
end
Group_Function3 (Where the problem occurs)
function [H] = Group_Function3(V)
prompt = {V};
title = ['Variable Ratings For' Group_Function1(answer{1})];
h = inputdlg(prompt, title, [1 80])';
end
The Problem
For 'Group_Function3' I want the prompt to include the users inputs from 'Group_Function1' so that when the prompt comes up to input the answers I know which vehicle I am entering for.

Answer 1

Each function runs in its own workspace, it means it does not know the state or content of variables outside of it. If you want a function to know something specific (like the name of a car), you have to give that to the function in the input parameters. A function can have several inputs parameters, you are not limited to only one.
Before going into the Group_Function3 , I'd like to propose a new way for Group_Function1.
Group_Function1 :
You run a loop to ask independantly for each car name. It is rather tedious to have to validate each dialog boxe. Here is a way to ask for the 4 car names in one go:
replace the beginning of your script with:
title1 = 'Cars';
prompt1 = {'How Many Cars (4): '};
answer1 = inputdlg(prompt1, title1 );
nCars = str2double( answer1{1} );
CarNames = getCarNames(nCars) ; % <= use this function
% [N] = Group_Function1(Q1); % instead of this one
and replace Group_Function1 with:
function CarNames = getCarNames(nCars)
title = 'Car Names';
prompt = cellstr( [repmat('Name of car #',nCars,1) , sprintf('%d',(1:nCars)).'] ) ;
CarNames = inputdlg( prompt, title, [1 80] ) ;
end
Now CarNames is a cell array containing the name of your 4 cars (as your variable N was doing earlier. I recommend sligthly more explicit variable names).
You can run the rest of your code as is (just replace N with CarNames, and Q1 with nCars).
Group_Function3 :
when you get to the Group_Function3, you have to send the current car name to the function (so it can use the name in the title or prompt). So replace your Group_Function3 as following (we add an input variable to the function definition):
function H = Group_Function3( V , thisCarName )
prompt = {V};
title = ['Variable Ratings For' thisCarName];
H = inputdlg(prompt, title, [1 80])';
end
and in your main script, call it that way:
for h = 1:nCars
thisCarName = carNames{h} ;
H = Group_Function3( V , thisCarName ) ;
% ...
% anything else you want to do in this loop
end