Function 'subsindex' is not defined for values of class 'datetime'.

I have a simplest possible csv file but still cannot plot(test.X,test.Y) with the above message. Please advise.

[Matt Dickson]

What are you trying to plot? Are you plotting the values in the Y col vs the dates in the X col? How are you loading the csv file into the workspace?

[Stephen23]

This is the format of the file:

X,Y
1/3/09,1.00
1/5/09,0.00
1/7/09,0.00
1/9/09,14.00
1/11/09,106.00
1/13/09,116.00
1/15/09,136.00
1/17/09,109.00
1/19/09,120.00
1/21/09,115.00

That first column is certainly not simple. As that column does not consist simple number, how are they supposed to be interpreted?

[Matt Dickson]

You'll have to read them in as strings, then you can make them into datetime objects if you want. To get the entire csv file as a cell array, load it into the workspace as

[~,~,test] = xlsread('test.csv');

You'll now have a 2x11 cell array with the first col as strings for the dates and the second col as the values next to them. From there, you have to decide what you want to do. Your post implies you wanted to plot the data; are you plotting the values against the dates?

[alpedhuez]

Working on it.

[Walter Roberson]

If you do wish to use the dates as the X axis, then which MATLAB release are you using?

[Stephen23]

See also earlier question and discussion:

https://www.mathworks.com/matlabcentral/answers/405315-removing-hours-and-minutes-from-date

Answer 1

[Walter Roberson]

With sufficiently new MATLAB:

T = readtable('test.csv');
plot(T.X, T.Y)

[Matt Dickson]

To make sure the year stays as 2009, add this line between reading and plotting:

T.X.Year = T.X.Year + 2000;

[Walter Roberson]

We have no reason to expect it to refer to 2009 instead of (say) 1609. So instead do

T.X.Format = 'MM/dd/yy';

[alpedhuez]

Working on it.

[Matt Dickson]

It's not because people may confuse it with 1609, as you said, but because the plot as you showed would simply show the year as "9", not "09". Hence, if you want the date with a normal year format with the year at the bottom and not part of each tick mark, you do need to add 2000 to each year.

[Walter Roberson]

Ah, I had never noticed the XRuler.SecondaryLabel for datetime plots before. And the appropriate code all appears to be built-in, so I can't poke through it :(

Answer 2

[OCDER]

FID = fopen('test.csv');
Data = textscan(FID, '%D%f', 'Delimiter', ',', 'Headerlines', 1);
fclose(FID);
Data{1}.Year = Data{1}.Year + 2000; %Assuming you want 2009, etc.
plot(Data{1}, Data{2})