Matlab coding issue with "fprintf" function

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Adam Scott 2021-2-4

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评论： Star Strider 2021-2-5

Hi, i am trying to print the output of my code into columns and now the results print but not in their respective columns. It prints from the first value of my first variable to its last, then the 1st value of my 2nd variable to its last, etc. I want them to print in their respective columns like the example below.

x v a

-------------

x1 v1 a1

x2 v2 a2

x3 v3 a3

but what i obtain is

x v a

-------------

x1 x2 x3

v1 v2 v3

a1 a2 a3

this is my code

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Answer 1

Star Strider 2021-2-4

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在 MATLAB Online 中打开

My version of MATLAB will not run images of code, only actual code, and I have no desire to type all of that in.

See if:

fprintf('%-4.2f %-42.f %-4.2f %-4.2f', output.')

does what you want. (Note the transposition: (.') for complex data or (') otherwise.)

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Walter Roberson 2021-2-5

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Fixed-width formats are not magic. They do not look at all of the data ahead of time and automatically expand the width to be used for a column according to the maximum width that any element of the column will need. If you want everything to line up, you need to use a width that accomodates the maximum range including possible negative sign.

Also you used a negative width. That tells MATLAB to use left justification with the field.

1.00_

-1.00

Whereas you probably wanted

1.00

-1.00

which you can only get with right justification or 0 fill.

%Problem 1-A

%data given

m=4;

k=2500;

c=0;

x0=0.1;

xd0=-10;

n=50;

dt=0.01;

t=[0:dt:(n*dt)];

%natural frequency

wn=sqrt(k/m);

%damping ratio

tho=c/(2*sqrt(k*m));

%Calculating displacement

if tho==0 %undamped

xt=(xd0/wn)*sin(wn*t)+x0*cos(wn*t);

xdt=xd0*cos(wn*t)-x0*wn*sin(wn*t);

xddt=-x0*wn*sin(wn*t)-x0*wn^2*cos(wn*t);

end

plot(t,xt,t,xdt,t,xddt);

legend('Displacement','velocity','acceleration')

title('System responses')

xlabel('time(s)')

ylabel('x(t), v(t),a(t)')

grid on

output = [t';xt';xdt';xddt'];

fprintf('t x v a\n')

t x v a

fprintf('----------------------------------\n')

----------------------------------

fprintf('%6.2f %6.2f %6.2f %6.2f\n',output.')

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50 0.10 -0.00 -0.10 -0.20 -0.28 -0.35 -0.39 -0.41 -0.41 -0.37 -0.32 -0.25 -0.16 -0.06 0.05 0.15 0.24 0.31 0.37 0.40 0.41 0.39 0.35 0.29 0.21 0.11 0.01 -0.09 -0.19 -0.27 -0.34 -0.39 -0.41 -0.41 -0.38 -0.33 -0.26 -0.17 -0.07 0.03 0.13 0.23 0.30 0.36 0.40 0.41 0.40 0.36 0.30 0.22 0.13 -10.00 -10.31 -9.97 -9.02 -7.51 -5.53 -3.20 -0.68 1.89 4.34 6.52 8.29 9.55 10.21 10.24 9.63 8.43 6.70 4.55 2.12 -0.44 -2.97 -5.32 -7.34 -8.90 -9.91 -10.30 -10.06 -9.18 -7.74 -5.81 -3.52 -1.02 1.55 4.02 6.25 8.08 9.41 10.16 10.27 9.75 8.62 6.95 4.86 2.46 -0.10 -2.64 -5.03 -7.10 -8.73 -9.81 -62.50 -61.18 -56.05 -47.43 -35.87 -22.08 -6.91 8.68 23.74 37.32 48.58 56.81 61.52 62.40 59.41 52.71 42.74 30.12 15.62 0.15 -15.33 -29.86 -42.53 -52.55 -59.31 -62.38 -61.57 -56.94 -48.76 -37.55 -24.01 -8.97 6.62 21.80 35.63 47.24 55.92 61.11 62.51 60.02 53.80 44.24 31.92 17.62 2.22 -13.31 -28.02 -40.98 -51.40 -58.62 -62.20

Adam Scott 2021-2-5

在 MATLAB Online 中打开

@Walter Roberson

Maybe i explained myself wrong. The desired output i want is obtained in the example below ! I just want to adapt it to mine so that i can obtain a table well organised as below.

---------------------------

%Given time span 
deltaT = 0.01; 
n = 50; 
tspan = 0:deltaT:n*deltaT; 
%Given initial conditions 
y0 = [100e-3 -10e-3]; 
m = 4; 
k = 2500; 
c = 0; 
%Numerical solution of differential equations 
[T1,Y1] = ode45(@(t,y) coupled_diff(t,y,m,k,c),tspan,y0); 
t = T1; 
x = Y1(:,1); 
v = Y1(:,2); 
a = (-k*x - c*v)/m; plot(t,x,t,v,t,a); 
output = [t';x';v';a']; 
fprintf('t      x         v         a\n')    
fprintf('----------------------------------\n') 
fprintf('%-4.2f   %-4.2f    %-4.2f    %-4.2f\n',output) 
%Function definition 
function f = coupled_diff(t,y,m,k,c) 
f  = zeros(2,1);     
f(1) = y(2); 
f(2) = (-k*y(1)-c*y(2))/m; 
end

****Here we can see that the value for time (t) starts from 0 and goes up. That is the relationship i want for my example. I want the time to start from 0 and to see the respective displacement, velocity and acceleration. ***

Adam Scott 2021-2-5

Your solution is working. The error was on my side.

Thank you for your time and support. It is really appreciated.

Star Strider 2021-2-5

As always, my pleasure!

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Matlab coding issue with "fprintf" function

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