How to plot this matrix?
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I am trying to plot two different lines on the same graph and am having some trouble. This is the code i have written so far:
n = 16.7185;
for i = 1:1:40
n = n+0.1;
T2 = T1*n^l;
T4 = T3/n^l;
efficiency = 1-1/n;
m(i,2)= W/(T3-T4-T2+T1)/Cp;
q(i,2) = W/efficiency;
plot(i,m(i,2));
plot(i,q(i,2));
hold all
end
hold off
grid on
The values for l,W,T1 and T3 are predefined and I am getting no erroes. Where exactly am I going wrong? When i try to see the plot it comes out as blank and when I go into the detailed view to modify the axes I see that it is trying to plot a line for each data point but I don't understand why it would do that.
1 个评论
Vidhan Malik
2016-2-13
编辑：Geoff Hayes
2016-2-13
采纳的回答
Geoff Hayes
2016-2-13
Vidhan - what are the values for your predefined variables? If I randomly assign some numbers (to them) then I see two lines. Once the loop has finished, what does the data in the arrays m and q look like?
Note that each time that you call plot, the code is creating a graphics object on the parent figure. Since you are collecting all of your data into two arrays, then you may as well just plot the data once the arrays have been populated. For example,
m = zeros(40,2);
q = zeros(40,2);
n = 16.7185;
for k = 1:1:40
n = n+0.1;
T2 = T1*n^l;
T4 = T3/n^l;
efficiency = 1-1/n;
m(k,1) = n;
q(k,1) = n;
m(k,2)= W/(T3-T4-T2+T1)/Cp;
q(k,2) = W/efficiency;
end
figure;
hold on;
plot(m(:,1),m(:,2),'b.');
plot(q(:,1),q(:,2),'r.');
(Note that I replaced i with k since MATLAB uses i and j to represent the imaginary number. It is good practice to avoid using indexing variables with the same name.)
2 个评论
Vidhan Malik
2016-2-13
Geoff Hayes
2016-2-14
Vidhan - even with your pre-defined values, I still see two lines drawn (using the code from above).
更多回答（1 个）
Roger Stafford
2016-2-13
In http://www.mathworks.com/help/matlab/ref/hold.html Mathworks states that for 'hold all' "This syntax will be removed in a future release. Use hold on instead". Also you are applying it too late to catch the first 'm' point.
In any case it would be better to first accumulate 'm' and 'q' in arrays and then plot them afterwards all at once. You wouldn't need to do a 'hold' at all then.
for i = 1:40
....
end
plot(1:40,m,'r-',1:40,q,'g-') % Plot in red and green
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