multiplying scalar by matrix

73 visualizzazioni (ultimi 30 giorni)
Louisa Mezache
Louisa Mezache il 22 Set 2020
Modificato: the cyclist il 22 Set 2020
Hello,
I'm trying to plot the equations for I1 and I2 on the same graph, but nothing is showing up when I run the code. To avoid any matrix/scalar multiplication and division mistakes, I just added a period everywhere. The x-axis should be lambda, from 400 to 700 but the blank graph that shows up is from 0 to 1. I appreciate any help. I'm fairly new to Matlab, but I'm working on getting more practice. Below is my code. Please let me know if you need any more information.
lambda = 400:700;
h = 6.626e-34; %Planck's constant
c = 3e8; %speed of light
k = 1.380e-23; %Boltzmann's constant
T1 = 505.372; %preheat temperature in Kelvin
T2 = 449.817; %cooking temperature in Kelvin
I1 = (2*h*c^2 ./ lambda.^5) .* 1./(exp(h*c./lambda .* k .* T1) - 1); %spectral radiance at T1
I2 = (2*h*c^2 ./ lambda.^5) .* 1./(exp(h*c./lambda .* k .* T2) - 1); %spectral radiance at T2
plot(lambda,I1,lambda,I2)
Thank you,
Louisa

Risposta accettata

the cyclist
the cyclist il 22 Set 2020
Modificato: the cyclist il 22 Set 2020
In the exponentials, you missed an important set of parentheses, ensuring that you divide by the whole expression
(lambda .* k .* T)
Instead, you are dividing by lambda, and then multiplying by k and T.
You need
I1 = (2*h*c^2 ./ lambda.^5) .* 1./(exp(h*c./(lambda .* k .* T1)) - 1); %spectral radiance at T1
I2 = (2*h*c^2 ./ lambda.^5) .* 1./(exp(h*c./(lambda .* k .* T2)) - 1); %spectral radiance at T2
  3 Commenti
the cyclist
the cyclist il 22 Set 2020
Modificato: the cyclist il 22 Set 2020
You're welcome. FYI, this was fairly easy to debug by inspecting the variable values when you plotted them. The issue was that I1 and I2 were actually "Infinite". Then it was a matter of tracing back how that happened.
If you are not familiar with the debugging tools in MATLAB, take a look at this documentation.
Louisa Mezache
Louisa Mezache il 22 Set 2020
Got it! That's very helpful. Thank you, again!

Accedi per commentare.

Più risposte (0)

Categorie

Scopri di più su Programming in Help Center e File Exchange

Prodotti


Release

R2017b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by