Problem in Plotting graph.

I am a beginner of matlab , having simple problem. i want to make a graph by this program but not successful yet. kindly help me by identifying and rectifying the problem.

% Question Number 6

clc

clear

a=0.1;

p=120000;

t=288;

dax=0.1;

m=150;

r=287;

cp=1004;

row=1.45;

v(1)=300;

for i=1:2*m;

    v(i+50)=v(i);
end

for j= 1:5;

    dvx(j+1)=dvx(j)
end

dvx=-0.145*v(i)/(0.145+(0.1*v(i)*((v(i)/cp-v(i)/r)*(row/r))))

plot(v,dvx(j),'+');

[Marta Salas]

You have to define a value for dvx(1) to be able to run this for loop:

for j= 1:5;

    dvx(j+1)=dvx(j)
end

However, you redefine dvx after that. What are you trying to do?

[Marta Salas]

Note: there is a good reason for not using i & j as indexes in MATLAB http://matlab.wikia.com/wiki/FAQ#Why_is_6.2Ai_not_a_complex_number_in_my_program.3F

[Arif]

I Want to plot a graph between 'v' and 'dvx' . with the values of v are from 50 to 300 and accordingly resultant values of dvx.

Answer 1

[Marta Salas]

p=120000;
t=288;
dax=0.1;
m=150;
r=287;
cp=1004;
row=1.45;

v=50:300; 
dvx=-0.145*v./(0.145+(0.1*v.*((v./cp-v./r)*(row/r))))

plot(v,dvx,'+');

Is this what you want?

[Arif]

Thanks a lot for help.