Output data to text file

I have this code

H = 1;
h = 15;
l = 500;
g = 9.81;
n1 = 1;
n2 = 2;
n3 = 3;
L1 = (2*l)/n1;
L2 = (2*l)/n2;
L3 = (2*l)/n3;
T1 = (2*l)/(n1*sqrt(g*h));
T2 = (2*l)/(n2*sqrt(g*h));
T3 = (2*l)/(n3*sqrt(g*h));

t = 0;
x = 0:10:l;
k1 = (2*pi)/L1;
k2 = (2*pi)/L2;
k3 = (2*pi)/L3;
sigma1 = sqrt(g*k1*tanh(k1*h));
sigma2 = sqrt(g*k2*tanh(k2*h));
sigma3 = sqrt(g*k3*tanh(k3*h));

eta1 = (H/2)*cos(k1*x)*cos(sigma1*t);
eta2 = (H/2)*cos(k2*x)*cos(sigma2*t);
eta3 = (H/2)*cos(k3*x)*cos(sigma3*t);

figure
hold on
subplot(3,1,1);
plot(x,eta1)
title('n = 1');
subplot(3,1,2);
plot(x,eta2)
title('n = 2')
subplot(3,1,3);
plot(x,eta3)
title('n = 3');

I need to output the data into 3 text files with 2 columns where x = 1,2,3 for three modes respectfully. (n =1,2,3 are modes). How would I go about this?

[stozaki]

Hi,

I find the content on the next page useful.

Write Data to Text Files

Answer 1

[William Rose]

@Tyler Bodnarik,

On Matlab 2021, use writetable() or dlmwrite(). See help for each.

On Matlab 2018, use dlmwrite(), since writetable() was not yet in Matlab.

Use Matlab's aray capability to shorten your code.

I recommend that you rename variable l to xmax, since l and the numeral 1 look so similar in the Courier font used by Matlab.

Here is code that uses Matlab's array capability and creates the three files you requested.

H = 1;
h = 15;
xmax = 500;
g = 9.81;
n=1:3;                              %1x3 array
L=2*xmax./n;                        %1x3 array
T=2*xmax./(n*sqrt(g*h));            %1x3 array
t = 0;
x = 0:10:xmax;                      %1x51 array
k=2*pi./L;                          %1x3 array
sigma = sqrt(g*k.*tanh(k*h));       %1x3 array
eta=H/2*cos(k'*x).*cos(sigma'*t);   %3x51 array
figure
for i=1:3
    subplot(3,1,i);
    plot(x,eta(i,:))
    titlestr=sprintf('n=%d',i);
    title(titlestr);
    filename=sprintf('dataout%d.txt',i);
    dlmwrite(filename,[x',eta(i,:)']);
end

Good luck with your work.