My figure wont display a line

For some reason I am unable to produce a line to connect my data points on the plot shown below. Please help. Also, I am using version 2018a.

time_array = linspace(1,34,34);

plot(time_array(1:2),2,'-ob')

hold on

plot(time_array(3:32),0,'-ok')

plot(time_array(33:34),-2,'-ob')

Answer 1

[Geoff Hayes]

Hasan - look closely at your calls to plot

plot(time_array(1:2),2,'-ob')

The first input is an array of two elements but the second input is an array of one element. So what is happening here? If you change the code to

hPlots = plot(time_array(1:2),2,'-ob')

then hPlots will be an array of graphics objects that are created when you call plot for this data. Now when you run this code and since there is no semi-colon at the end of the line, you will see something similar to the following in the command window

hPlots =

  188.0033
  189.0033

This tells us that two graphics objects are being created and so we have two separate plots! And so this is why there is no line connecting the data points. You need to have a 1-1 mapping of x and y points as your inputs. You can easily fix this by just replicating the second input for as many elements in the first input array. Try the following

hPlots = plot(time_array(1:2),repmat(2,1,length(time_array(1:2))),'-ob')
hold on
plot(time_array(3:32),repmat(0,1,length(time_array(3:32))),'-ok')
plot(time_array(33:34),repmat(-2,1,length(time_array(33:34))),'-ob')

Now your data points shoudl be connected. (Note also how hPlots is a single graphics object handle.)

[Hasan Swain]

Thanks a lot Geoff! This was very helpful.