why my matlab didn't plot anything?
显示 更早的评论
So i tried to plot a graph using this code, but it won't plot anything. I believe my code is plotting a point but not a line and i don't know why
clear all
m = 85
g = 9.81
ti = 0
tf1 = 9
v(1)= -20
h = 1
c1 = 11
dv1 = @(g,c1,v,m) g-c1*v/m
while(ti<tf1)
v = v + dv1(g,c1,v,m)*h
ti = ti+h
plot(ti,v)
drawnow
end
采纳的回答
m = 85;
g = 9.81;
ti = 0;
tf1 = 9 ;
v(1)= -20;
h = 1;
c1 = 11;
dv1 = @(g,c1,v,m) g-c1*v/m;
k=1;
while(ti<tf1)
k=k+1;
v(k) = v(k-1) + dv1(g,c1,v(k-1),m)*h;
ti=ti+h;
plot(0:h:ti,v); drawnow
end
更多回答（1 个）
Start with something like this:
m = 85;
g = 9.81;
ti0 = 0;
tf1 = 9;
v0 = -20;
h = 1;
c1 = 11;
dv1 = @(g,c1,v,m) g-c1*v/m;
ti = ti0:h:tf1;
v = zeros(1,numel(ti));
v(1) = v0;
for k = 2:numel(ti)
v(k) = v(k-1) + dv1(g,c1,v(k-1),m)*h;
end
plot(ti,v)
Plotting one point at a time is generally unnecessary and cumbersome. When you plot single points that way with the default linestyle, they are not connected by lines. You could make the dots themselves visible by specifying a marker type other than the default, but storing the results and putting the plot statement outside the loop avoids the hassle and leaves you with vectors that can be used for other things if needed.
It's also generally good to avoid unnecessary while loops, using for-loops when the number of iterations is known beforehand. This avoids any chance of mistakes or unpredicted scenarios that could cause the loop to not terminate. Such an oversight isn't really a big risk with something this small, but it's something to keep in mind as your code gets more complex.
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