# How to code equation

2 views (last 30 days)
Cesar Cardenas on 24 Jan 2023
Commented: Cesar Cardenas on 3 Feb 2023
Hello, just wondering if this equation could be coded like this:
Any feedback will be greatly appreciated. Thanks
m = 10e-3
a = 0.05
c = 0.1
x(t) = m/a e^-(c/a)t

Sulaymon Eshkabilov on 24 Jan 2023
A couple of small errors have been corrected:
m = 10e-3;
a = 0.05;
c = 0.1;
x = @(t)(m/a)*exp(-(c/a)*t);
t = linspace(0,1.3);
plot(t, x(t))
xlabel('t')
ylabel('x(t)')
grid on
Cesar Cardenas on 27 Jan 2023
Thanks much for your help. I added another equation and would like to know how to plot both on the same graph? not sure about it. Thanks
m = 10e-3;
a = 0.05;
c = 0.1;
x = @(t)(m/a)*exp(-(c/a)*t);
x = @(t)(m/a)*1-exp(-(a/m)*t);
t = linspace(0,1.5);
plot(t, x(t))
xlabel('t')
ylabel('x(t)')
grid on

Torsten on 24 Jan 2023
Moved: Torsten on 24 Jan 2023
m = 10e-3;
a = 0.05;
c = 0.1;
x = @(t) m/a*exp(-c/a*t);
t = 0:0.01:2;
plot(t,x(t))
Cesar Cardenas on 27 Jan 2023
Thanks much for your help. I added another equation and would like to know how to plot both on the same graph? not sure about it. Thanks
m = 10e-3;
a = 0.05;
c = 0.1;
x = @(t)(m/a)*exp(-(c/a)*t);
x = @(t)(m/a)*1-exp(-(a/m)*t);
t = linspace(0,1.5);
plot(t, x(t))
xlabel('t')
ylabel('x(t)')
grid on

Sulaymon Eshkabilov on 27 Jan 2023
Put both functions in plot() command or use hold on:
m = 10e-3;
a = 0.05;
c = 0.1;
x1 = @(t)(m/a)*exp(-(c/a)*t);
x2 = @(t)(m/a)*1-exp(-(a/m)*t);
t = linspace(0,1.5);
plot(t, x1(t), 'r-', t, x2(t), 'b-.', 'linewidth', 2)
xlabel('\$t\$', 'Interpreter', 'latex')
ylabel('\$x(t)\$', 'Interpreter', 'latex')
legend('\$x_1(t)\$', '\$x_2(t)\$','Interpreter', 'latex', 'location', 'SE')
grid on
%% Alternative solution:
m = 10e-3;
a = 0.05;
c = 0.1;
x1 = @(t)(m/a)*exp(-(c/a)*t);
x2 = @(t)(m/a)*1-exp(-(a/m)*t);
figure
fplot(x1, [0, 1.5], 'r-', 'linewidth', 2)
hold on
fplot(x2, [0, 1.5], 'b-.', 'linewidth', 2)
xlabel('\$t\$', 'Interpreter', 'latex')
ylabel('\$x(t)\$', 'Interpreter', 'latex')
legend('\$x_1(t)\$', '\$x_2(t)\$','Interpreter', 'latex', 'location', 'SE')
grid on
Cesar Cardenas on 3 Feb 2023
Hello, thanks much for your response, really useful. Now, I'm trying to code these equations. This is my attempt. I would like to plot Cf vs x/L, but x/L as I have it shows me an error..the same with delta/x, not sure why? any help will be greatly appreciated. Thanks much.
Re = 0:500:1000;
x/L = 0:0.2:1;
Cf = 0.664*(Re)^-0.5;
delta/x = 5.0*(Re)^-0.5;

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