line in my graph does not show

this is my file . when i plot my function the figure wil occur but no line is showed in it. what did i do wrong. it is driving me crazy

clear all  clc          
format compact          

for x = 0:1:6;          

V = (5/3 * x^3) ;   

M = (5/4 * x^4);    
end 

plot ( x,V,x,M );       

and this is what i'm getting out of the plot

[Niki]

My graph was there and now it is gone. No idea what I hit or what I did. Any help is appreciated. I did not change my code.

[Voss]

@Niki: What happens if you run the code again?

If that doesn't work, post the code in a new question.

Answer 1

[Chad Greene]

The data you've created in the for loop is indeed shown as tiny little dots! Unfortunately, you've overwritten V and M with every iteration of the for loop, so all you're left with is the last set of entries: x=6, V=360, and M=1620. Look close and you'll see dots at those locations in the image you posted.

To do what you're trying to do in a for loop, try this:

x = 0:1:6; 
for k = 1:length(x) 
    V(k) = (5/3 * x(k)^3) ;   
    M(k) = (5/4 * x(k)^4);  
end
plot ( x,V,x,M );

But the above solution is inefficient, ugly, and generally bad practice. It'd be really slow if you had a big data set. A better way is to vectorize:

x = 0:1:6;  
V = (5/3 * x.^3) ;   
M = (5/4 * x.^4);  
plot ( x,V,x,M );

Notice that in the vectorized solution we had to switch to the dot operator .^ because with multiplication and powers the dot or no dot forms are equivalent to a dot product versus cross product.