Help with plot function!

I have a matrix of data named "D.data" and I can take sections of the matrix and assign them to a variable, like so:

A = D.data(:,89);

And I can plot two vectors taken from the initial data matrix like so:

plot(B,A)

However, when I want to take multiple rows from the starting matrix and combine them into one column vector, like this:

time = datestr(datenum(D.data(:,1:6)));

I cannot plot it anymore. It can be displayed like:

disp (time);

in which case it will display a list of times:

03-Dec-2011 05:28:36

03-Dec-2011 05:29:37

03-Dec-2011 05:30:38 ...

Why does "plot(time,A)" not work?

Here is the error it gives:

 ??? Error using ==> plot
 Invalid first data argument

 Error in ==> joan2>pushbutton1_Callback at 133
        plot(time,Klystron);

 Error in ==> gui_mainfcn at 96
        feval(varargin{:});

 Error in ==> joan2 at 43
    gui_mainfcn(gui_State, varargin{:});

 Error in ==>
 @(hObject,eventdata)joan2('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

 ??? Error while evaluating uicontrol Callback

Thank you in advance!

Answer 1

[Chad Greene]

Matlab knows how to plot numbers, not strings! So try

time = datenum(D.data(:,1:6));
plot(time,A)
set(gca,'XTick',[min(time):((max(time)-min(time))/5):max(time)]) % set array of tick labels
datetick('x',15,'keepticks') % displays datenums as strings we understand

[Chad Greene]

Above, the 5 in (max(time)-min(time))/5 simply sets evenly spaced ticks. And the 15 in datetick('x',15,'keepticks') is the display format. Type help datetick into the command line for more display options.

[Chad Greene]

These may also be useful:

http://www.mathworks.com/matlabcentral/fileexchange/27075

http://www.mathworks.com/matlabcentral/fileexchange/32359

[J]

This is great! Thank you very very very very much!

I realized soon after I posted the question that it (of course) couldn't plot strings, but I didn't know what else to do. So thank you!

[KRUNAL]

I have date in column 1 and time in column 2 and data in column three. I want to plot date/time against that data. Can anyone tell me how can I do it?

[Chad Greene]

KRUNAL, some combination of datenum and datevec may be the ticket. For a better answer, I recommend opening a brand new question. When you do, be specific about the format of your dates and times. When asking questions always be as specific as possible, and provide simplified examples when you can.