MATLAB: Plot shows empty display

MATLAB

I am using the following code to make a plot. However, I do not see the line being plotted. Why is this?

x = 0:100:1;
y = x.^2;
plot(x,y);

Best Answer

In this code, the first line has the effect of creating a variable "x", with just the scalar value 0.

This is because the second value represents the step size in the linearly spaced vector that we wish to create, and not the number of points.

Because of this, both "x", and "y" end up being scalar inputs to the "plot" function.

To rectify this, replace the first line with the following :

x = 0:1/100:1;
y = x.^2;
plot(x,y);

Related Solutions

MATLAB: Displaying names of multiple variables in a plot

Let us assume that you have following variables created in your workspace:

>> v1 = rand(10,1);

>> v2 = rand(10,1)+1;

>> v3 = rand(10,1)+2;

>> v4 = rand(10,1)+3;

>> v5 = rand(10,1)+4;

>> v6 = rand(10,1)+5;

>> v7 = rand(10,1)+6;

>> v8 = rand(10,1)+7;

>> v9 = rand(10,1)+8;

1. You can concatenate all the variables into a matrix and then you can plot them as you iterate over matrix of variables using "for" loop with "hold on" command. To accomplish that you can execute following code:

>> variables = [v1,v2,v3,v4,v5,v6,v7,v8,v9]; % This creates (10-by-9) matrix containing variables as individual columns. All the variables should have same number of values else MATLAB will throw an error.

>> for i = 1:9

>> plot(dates, variables(:,i)); % Variables are plotted column by column.

>> hold on;

>> end

>> varNames = {'y = IEI','y = IEF','y = SHY','y = TLH','y = TLT','y = TIP','y = AGZ','y = CIU','y = HYG'}; % Create a cell array of strings for legend

>> legend(varNames, 'Location', 'SouthWest'); % Provide the cell array as an argument to "legend" function. Number of entries in cell array should be same as number of variables.

>> xlabel('Date');

>> ylabel('Normalized Price');

>> title('Normalized Asset Prices and Benchmark');

>> datetick('x');

>> grid on;

>> hold off;

2. You can concatenate all the variables into a matrix and provide that matrix as input to the plot function which will plot the data for you. You do not have to use "hold on" command in this approach. To accomplish this you can execute:

>> plot(dates,variables); % Variables are plotted column by column.