How do I plot a selective range of x-axis values

I am a new user of MATLAB. Currently I have this in my script:

figure

subplot(2,2,1)

plot(t/60,mass)

grid on

title('Mass dried')

xlabel('Time, t (min)')

ylabel('Mass dried, g')

This plots time in minutes on the x-axis, where "t" is the time vector in seconds returned from the function pdepe(m,@solnpde,@solnic,@solnbc,r,t,options). The solution to the pde is from t = 0 to t = 1800.

Please advise how I can plot the graph for values of t from:

1. t = 0 to t = 600

2. t = 600 to t = 1200.

Many thanks,

Doug

Answer 1

[Naz]

your 't' and 'm' must be the same size; open the variable 't' from Workspace and look what index contains the value of ~600. Let's say the index is 20. Thus, you want to use a part of 'time' array from index 1 to 20. Similarly, you find what index corresponds to value of 1200. If it you found it to be equal let's say 40, then you need to use t[21:40]

subplot(2,1,1)

plot(t(1,1:20),m(1,1:20));

subplot(2,1,2)

plot(t(1,21:40),m(1,21:40));

Of course, there is a way to find corresponding indecies automatically, but if you are planning to use it once, it is easier just to look up for the each index yourselves.

I think here is the way to find'em automatically:

t_temp=t;

t_temp=t_temp-600;

t_temp=abs(t_temp);

index600=find(t_temp==(min(t_temp)),1,'first');

same for the other:

t_temp=t;

t_temp=t_temp-1200;

t_temp=abs(t_temp);

index1200=find(t_temp==(min(t_temp)),1,'first');

subplot(2,1,1)

plot(t(1:index600),m(1:index600));

subplot(2,1,2)

plot(t(index600:index1200),m(index600:index1200));

Now, I hope, this answer is deserved to be accepted.

[Douglas]

Thanks Naz! Just one question: In you line:

plot(t(1,21:40),m(1,21:40));

I can undertand the "21:40" in the second index of t and m. Please explain what the first index of "1" means.

Thanks, Doug

[Naz]

t(1,21:40) is 1st row, colums 21:40. This is more general implementation. Since your t and m are only arays (one row), you probably can ignore the '1'. That is:

plot(t(21:40),m(21:40));

[Douglas]

Thanks

Answer 2

[Kevin Geib]

Hey,

another Option if you dont want to change the Plot command itself and see a specific x/y Plot is to limit your axis.

plot(t/60,mass)

grid on

title('Mass dried')

xlabel('Time, t (min)')

ylabel('Mass dried, g')

xlim([0 60])

same can be done with y-axis

ylim([0 100])

Answer 3

[Fangjun Jiang]

t=0:1800;
mass=t;

index=1:600;
figure(1);plot(t(index)/60,mass(index));

index=601:1201;
figure(2);plot(t(index)/60,mass(index));

Answer 4

[Tahmid Rahman]

 x=1:0.1:100
if x<20
y1=2*sin(x);
elseif 20<=x , x<40;
y2=cos(3*x);
elseif 40<=x , x<60;    
y3=sin(0.3*x);
elseif x<=60
y4=8*sin(x);
elseif y<6
y5= 6;

need to draw a graph for each y condition.