How can I solve the error for plot?

Hi all,

I having the issue of plotting graph. I would be grateful that those who can solve the problem. Thanks!

%% Initialize Input
K = 1*(10^-9); % Carrying Capacity of Brain Tumor
C0 = 40000; % Initial Brain Tumor Population Size
r = 4.31*(10^-3); % Growth Rate of Brain Tumor Cells

%% Model Data
t = 365; % Time in Days
C(1) = C0;
% Calculating Brain Tumor Population 
for t=1:1:t-1
    C(t+1) = (K*(C0*exp(r*t)))/(K-C0+C0*exp(r*t));
end
hold on
nvec = 1:1:t;

%% Graph Plotting
figure(1)
title( 'Brain Tumor Population Against Time' )
xlabel('Time (Days)')
ylabel('Brain Tumor Population (cells)')
plot(nvec,C,'--bo','LineWidth',0.5,'MarkerSize',5,'MarkerEdgeColor','black')
grid
hold on

Above here is the code and the error is stated as below

Error using plot

Vectors must be the same length.

Error in Untitled (line 24)

plot(nvec,C,'--bo','LineWidth',0.5,'MarkerSize',5,'MarkerEdgeColor','black')

Answer 1

[KSSV]

clc; clear all ;
%% Initialize Input
K = 1*(10^-9); % Carrying Capacity of Brain Tumor
C0 = 40000; % Initial Brain Tumor Population Size
r = 4.31*(10^-3); % Growth Rate of Brain Tumor Cells
%% Model Data
t = 365; % Time in Days
C = zeros(t,1) ;
C(1) = C0;
% Calculating Brain Tumor Population 
for i=2:1:t-1
    C(i+1) = (K*(C0*exp(r*i)))/(K-C0+C0*exp(r*i));
end
hold on
nvec = 1:1:t;
%% Graph Plotting
figure(1)
title( 'Brain Tumor Population Against Time' )
xlabel('Time (Days)')
ylabel('Brain Tumor Population (cells)')
plot(nvec,C,'--bo','LineWidth',0.5,'MarkerSize',5,'MarkerEdgeColor','black')
grid
hold on

Answer 2

[Walter Roberson]

t = 365; % Time in Days

You set a variable t to 365

for t=1:1:t-1

You set up a for loop. The upper limit is t-1 which is 365-1 so the upper limit is 364. The loop control variable is named t which will cause the t = 365 to be overwritten. Each iteration of the loop, t will be assigned a new scalar. On the last iteration t = 364 will be in effect.

        C(t+1) = (K*(C0*exp(r*t)))/(K-C0+C0*exp(r*t));

C(t+1) is written to, and t is up to 364, so at the end, C(365) will be written to.

nvec = 1:1:t;  

After the for loop, t has the last value it was assigned, so t = 364. So nvec is 1 to 364.

plot(nvec,C,'--bo','LineWidth',0.5,'MarkerSize',5,'MarkerEdgeColor','black')

nvec is 364 long, C is 365 long.

You would not have had this problem if you had not re-used t as a variable name for different purposes.