Beginner in matlaB i need lil help

[Casablanca]

hello everyBody..
am a beginner in MATLAB i need lil help in the equation blew.. and if anyone has any tutorial for MATLAB i'll b more than welcome to accept them :P

y=e^x . cos x

plot : pi greater than x greater than 0
then plot : -pi smaller than x smaller than one

then combine the two graphs

i tried to do it but i get a lot of errors,,

my trial :
x=0:pi;
y=exp(x)* cos(x)
subplot (3,1,1)
plot (x,y)

x1=-pi:0;
y1=exp(x)* cos(x)
subplot (3,1,2)
plot (x1,y1)

subplot(3,1,3)
plot (y,y1)


=S

thanks in advance..

 

[ApexOfDE]

Your problem is that: in the first line, you declare x as an array. In the second line, you force MATLAB to calculate the exp and cos value for each member of x array. Therefore, MATLAB throws error because exp and cos funtion in MATLAB don't know how to do that but they only accept 1 value for argument per calculations.. To avoid this problem, you should use loop. For example:

x=0:0.01:pi;

for j = 1 : length(x)              // for loop
    y=exp(x(j))* cos(x(j));     // pick member x(j) to calculate
end;

plot (x,y)

//x(A) will give you value of Ath member of array x (A is integer and smaller than size of x).

----------
Loop is crucial concept for programming that you must obtain, such as FOR loop, WHILE loop, DO loop.

For more information about operators and functions in matlab, check FUNCTION REFERENCE in MATLAB help section.

Hope this help you.

 

[oswaler]

Hello and welcome to MATLAB! It's great that you're starting to learn this powerful tool. First of all, I recommend checking out the official MATLAB website for tutorials and resources. They have a lot of helpful information for beginners.

Now, let's take a look at your code. It seems like you're on the right track, but there are a few things that need to be corrected. First of all, you should use the ".*" operator when multiplying arrays, instead of just "*". So your code for y and y1 should be:

y = exp(x).*cos(x);
y1 = exp(x1).*cos(x1);

Also, your second subplot should have x1 as the x-axis, not x. So it should be:

subplot(3,1,2)
plot(x1,y1)

Finally, to combine the two graphs, you can simply use the "hold on" command before plotting the second graph. So your final code should look like this:

x = 0:pi;
x1 = -pi:0;
y = exp(x).*cos(x);
y1 = exp(x1).*cos(x1);

subplot(3,1,1)
plot(x,y)
hold on
subplot(3,1,2)
plot(x1,y1)
subplot(3,1,3)
plot(x,y,x1,y1)

I hope this helps and good luck with your MATLAB journey!