# Problems using Plot function

1 次查看（过去 30 天）
Hi,
I am trying to use the plot function, however, there is no line visible on the graph. lets say, I have
A=[1.1,1.2,1.3];
B=[2.1,2.2,2.3];
C=[3.1,3.2,3.3];
What I want is a plot of [1:3:1] on the X axis and values A(1),B(1),C(1) plotted with respect to point 1, A(2),..C(2) with respect to 2 and A(3)..C(3) with respect to point 3 on X axis.
I thought I would first declare a 3X3 zero matrix and subsequently save all the values of A B C in this array, and try to plot it. No matter what I am doing, I am getting a null plot.
A=[1:3];
B=[4:6];
C=[5:3];
for i=1:3
f(i)=A(i)^2;d(i)=5*B(i);v(i)=A(i)+B(i);
plot (i,f(i),d(i),v(i))
hold on
end

### 采纳的回答

Walter Roberson 2023-6-5
You are plotting one point at a time. By default, plot() does not put in any markers, and plot() can only draw lines when there are at least two adjacent finite values.
You should postpone the plot() until after the loop.
Also, 5:3 is the same as 5:1:3 . The first element is greater than the last element and the increment (1) is positive, so the result of 5:3 is empty.
Note also that plot(VALUE1,VALUE2,VALUE3,VALUE4) would be treated more like plot(VALUE1,VALUE2), plot(VALUE3,VALUE4) -- that is, you are asking to plot i against f(i), and to plot d(i) against v(i)
##### 1 个评论显示 无隐藏 无
Thanks Walter. I am new to MATLAB to be honest... Appreciate your help.

### 更多回答（1 个）

Pramil 2023-6-5
If you want to plot all A B C on the same plot you can use hold on like this :
A=[1.1,1.2,1.3];
B=[2.1,2.2,2.3];
C=[3.1,3.2,3.3];
X = 1:3;
xlabel('X');
ylabel('Value');
plot(X,A);
hold on
plot(X,B);
plot(X,C);
hold off ##### 1 个评论显示 无隐藏 无
Hi Pramil
thanks for the help. Lemme see if this suits my needs.

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