How to plot a function for different values of input parameter in a function

Hi,

Please, how do I create a procedure/function such that it carries \xi as an input and use it to plot r for different values of \xi. I have attached my code.

Answer 1

[Torsten]

Just define xi as a column vector of values, e.g.

xi = [0.03 0.06].';         %  activity parameter

[University Glasgow]

Thank you. But how do I call it in a function r then? For instance, if I want to plot for both 0.03 and 0.06 on the same figure?

[Torsten]

I don't understand.

In your code, both graphics (for xi=0.03 and xi =0.06) appear in the same figure if you leave the rest of your code unchanged.

[University Glasgow]

I received this erro: Arrays have incompatible sizes for this operation.

Error in qfordifferentxi (line 21)

r=q-(1-alpha)*tan(q)+(alpha3*xi*alpha/eta1)./(4*k1*q.^2/d^2-alpha3*xi/eta1).*tan(q);

[Torsten]

Did you use xi as column vector ?

Try what you get with elementwise multiplication of a column vector with a row vector.

r = rand(1,3);
xi = rand(2,1);
r.*xi

ans = 2×3

0.3904 0.0027 0.3068 0.2633 0.0018 0.2069

%% initialization
clear
clc
close all


%% Model parameters
global k1 eta1 alpha3 gamma1 d xi
k1 = 6*10^(-12);            %  elastic constant
eta1 = 0.0240;              %  viscosity
xi = [0.03 0.06 0.09].';    %  activity parameter
alpha3 = -0.001104;         %  viscosity
gamma1 = 0.1093;            %  viscosity
Theta = 0.0001;
d = 0.0002;


%% r(q) from matlab
alpha=1-alpha3^2/gamma1/eta1;
q=0:0.01:(5*pi);
r=q-(1-alpha)*tan(q)+(alpha3*xi*alpha/eta1)./(4*k1*q.^2/d^2-alpha3*xi/eta1).*tan(q);
% Plotting r(q)
figure
plot(q,r)
xlabel('q')
ylabel('r(q)')
axis([0 5*pi -20 20])

[University Glasgow]

I used xi = [0.03, 0.06] as justed

[Torsten]

I don't understand. My answer was

Just define xi as a column vector of values, e.g.

xi = [0.03 0.06].';         %  activity parameter

[University Glasgow]

Is working now. Thank very much. I didn't define it as a row vector.

[Torsten]

xi = [0.03, 0.06] is a vector, but a row vector.

[University Glasgow]

I mean I didn't do that before. Is actually working now.

But I tried to apply the same to my general code, it failed.

[Torsten]

%% initialization
clear 
clc
close all


%% Model parameters
global k1 eta1 alpha3 gamma1 d N Phi xi h A B C G
k1 = 6*10^(-12);            %  elastic constant
eta1 = 0.0240;              %  viscosity
xi = [-0.02 0.01 0.0].';                   %  activity parameter
alpha3 = -0.001104;         %  viscosity
gamma1 = 0.1093;            %  viscosity
Theta = 0.0001;
d = 0.0002;


%% Extract r(q) data from maple
%rqdata= xlsread('rqdata.xlsx');
%rq= rqdata(:,2);
%qsize = rqdata(:,1);

%% r(q) from matlab
alpha=1-alpha3^2/gamma1/eta1;
q=0:0.001:(5*pi);
r=q-(1-alpha)*tan(q)+(alpha3*xi*alpha/eta1)./(4*k1*q.^2/d^2-alpha3*xi/eta1).*tan(q);

% Plotting r(q)
%figure
%hold on
%plot(qsize,rq, 'r', MarkerSize=2)
plot(q,r, 'b--', MarkerSize=2)
xlabel('t (seconds)')
ylabel('\theta(d/2,t)(rad)')
legend('maple', 'matlab')
axis([0 5*pi -20 20])

[University Glasgow]

Thank you Torsten. This is actually working fine. But I have a different problem now. This is just part of my codes. I didn't wanna post all code. I thought using this as an instance could solve my problem.

In the attached file,I also wanna plot theta_sol and v_sol for xi = [0.03 0.06].'; but I received an error: Error in Case1_Ijuptilk_130822>lcode1 (line 147): rhsode(N,1) = (G/(h^3))*(-Phi + 3*theta(1) - 3*theta(2) + theta(3)) + (C/(h^2))*(v(2) -2*v(1)+ 0)

Please could you me check it out.