Solution of Growth problem

The function will take in two inputs and return one output. The function will be assessed by running the code: "yt=grow_population(y0,t);" for chosen values of a vector y0 and a scalar t. The vector y0 is a 6 X 1 vector that contains the initial populations of the 6 cities from the map (the first entry is A, the second is B, etc). The scalar t determines how many years of growth to compute. The change in city populations resulting from population growth can be found in the image above.

Inputs:

1. a vector of size 6 X 1 for the initial population sizes of the 6 cities (the first entry is A, the second is B, etc)
2. a scalar value for the number of years

Outputs:

1. a vector of size 6 X 1 that gives the population sizes resulting from t years of growth.

How did I think ?

function yt = grow_population(y0, t)
% y0 is a 6 x 1 vector of initial city populations

y0 = [100; 300; 500; 125; 100; 200];
% t is the number of years of growth    
t = 3;
% Defining growth factors from a to f
a = 1.0;
b = 0.8;
c = 1.1;
d = 1.1;
e = 1.3;
f = 0.9;
% Creating a vector of growth factors
variables = [a; b; c; d; e; f];
% Calculating population growth
yt = (y0 .* (variables.^t));
% Displaying the result
disp('The population yt is: ');
disp(yt);
end

What is the problem in here ? Thank you for helping.

Answer 1

[Sam Chak]

% y0 is a 6 x 1 vector of initial city populations
y0  = [100; 300; 500; 125; 100; 200];
% t is the number of years of growth    
t   = 3;
grow_population(y0, t)

The population yt is: 
  100.0000
  153.6000
  665.5000
  166.3750
  219.7000
  145.8000

function grow_population(y0, t)
    % Defining growth factors from a to f
    a = 1.0;
    b = 0.8;
    c = 1.1;
    d = 1.1;
    e = 1.3;
    f = 0.9;
    % Creating a vector of growth factors
    variables = [a; b; c; d; e; f];
    % Calculating population growth
    yt = (y0 .* (variables.^t));
    % Displaying the result
    disp('The population yt is: ');
    disp(yt);
end

[Sam Chak]

Hi @Oskar S.

The grow_population(y0, t) function is dependent on two variables, y0 and t. This means that we must provide the values of y0 and t before invoking the grow_population(y0, t) function to perform calculations and show the result.

In your code, the values for y0 and t are located within the function, which is not the correct approach. Therefore, I have relocated them 'outside' of the function, where you can either include them in a script or directly execute them in the Command Window. Both approaches are acceptable.

[Oskar S.]

Thank you very much Sam

[Sam Chak]

You are welcome @Oskar S.. You can also learn from @Aquatris's approach. 👍

Answer 2

[Aquatris]

You overwrite the y0 and t variable within the function with this code:

y0 = [100; 300; 500; 125; 100; 200];
t = 3;

So the user entered values are ignored completely. Remove that from your function cause it should be defined by the user while calling the function.

Otherwise assuming your equation is correct, seems to work fine. Also you might want to add the number of years to your disp call within the function.

y0 = [100; 300; 500; 125; 100; 200];
yt = grow_population(y0,3);

The population yt after 3 years is: 
  100.0000
  153.6000
  665.5000
  166.3750
  219.7000
  145.8000

yt = grow_population(y0,4);

The population yt after 4 years is: 
  100.0000
  122.8800
  732.0500
  183.0125
  285.6100
  131.2200

function yt = grow_population(y0, t)
% y0 is a 6 x 1 vector of initial city populations
%% removed y0 here
%% remove t here
% Defining growth factors from a to f
a = 1.0;
b = 0.8;
c = 1.1;
d = 1.1;
e = 1.3;
f = 0.9;
% Creating a vector of growth factors
variables = [a; b; c; d; e; f];
% Calculating population growth
yt = (y0 .* (variables.^t));
% Displaying the result
fprintf('The population yt after %.d years is: \n',t);
disp(yt);
end

[Oskar S.]

Thank you very much