Creating transparent rectangles when x values are times with dates

I understand how to use the patch function to create a shaded transparent rectangle when the x and y values are just numbers. For example, the code

plot([1 2],[2 1])  

x = [1.25 1.5 1.5 1.25];

y = [1 1 1.75 1.75];

p=patch(x,y,'r');

set(p,'FaceAlpha',0.5);

creates a graph with the plotted line and a transparent red rectangle. My actual plot has the x values (which are a time and date) exported from excel, and then converted to matlab date and time by using datetime and stored in the vector Time. After plotting my data, I tried to do something like this to add the shaded rectangle:

x = [Time(1) Time(2) Time(2) Time(1)];

y = [30 30 35 35];

p=patch(x,y,'r');

set(p,'FaceAlpha',0.5);

This gives me the error: "Error using patch. Vectors must be the same length." The vectors x and y are both length 4, so I don't understand why I get this error. Since it worked in the simple example, I am assuming it has something to do with the x values being in the datetime form.

[Geoff Hayes]

Rosalie - can you give an example of your Time vector? How have you created it, what are the dimensions, etc.? Also, what do the following return

 class(x)

and

 size(x)

[Rosalie Siciliano]

This is how I created the Time vector:

Time = xlsread('timesheet.xlsx', sheet, 'E:E'); %load log from excel file
  Time = datetime(Time,'ConvertFrom','excel'); %converts to matlab date and time

The cells of the column in the excel file that it imports are in the format month/day/year time. For example: 10/9/2015 2:37:00 PM. After converting using datetime, it is in the form 09-Oct-2015 14:37:00.

The value in the workspace for Time is 68x1 datetime.

for class(x):

ans =

datetime

For size(x):

ans =

       1     4

[Geoff Hayes]

Rosalie - according to patch, the x input array can only be of type single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64. In your case, you are using a datetime data type. You may need to convert that time vector to a numeric equivalent.

[James]

Digging some into the source code for stairs, it looks like there's an undocumented function to do this: matlab.graphics.internal.makeNumeric.

[XData, YData] = matlab.graphics.internal.makeNumeric(axis_handle, XData, YData);

Like all undocumented/internal functionality, your mileage may vary and it's subject to change at any time.

[Benjamin Kraus]

The documented function to use is ruler2num.

Answer 1

[James Uber]

I had the same problem using patch. fill() has no such limitation with date time axes, so perhaps that will work for you as well.

[Alan Bindemann]

Thanks, fill works much better than rectangle as it supports datetime values.

Answer 2

[Jan]

Please try to convert the time to a numerical format:

TimeNum = datenum(Time);

Or create it directly with x2mdate

TimeNum = x2mdate(xlsread('timesheet.xlsx', sheet, 'E:E'));

Then plotting should work. To get rid of the ugly axis lables, use datetick.