plot date from excel file

hi all, I am trying to plot power vs time in my program, these values are taking from excel file, but I am having different values for the time compare with values in excel, the time format is (HH:MM)and my code is:

 [num,T,vT] = xlsread(excle.xls,'Sheet1');      % reading excel
    x = num(:,1);                               % Time column
    y = num(:,4);                               % power column  
    plot(handles.axes,x,y);

how can I over come this issue ??? please help and advice...

[Conrad]

Can you give a concrete example of what the time looks like in Excel and then in Matlab?

[Sumit Tandon]

Not sure if I understand the question correctly. Are you having issues with the FORMAT of date in Excel vs MATLAB? You could use functions like DATENUM or DATEVEC to change the format and then plot as per your requirements.

[Samer Husam]

conrad: the time value is read from MATLAB it something like: 12:00, 12:15, 12:30 and so on. when I use the code that I post above, I get numeric values like 0.5, 0.51... so how can I display the time values from the excel ??

LukeS: I have tried to use the datenum but what I couldn't get it correctly, can you please show me how to use it ?

Answer 1

[Thomas]

Something like this

x={'12:00','12:15','12:30','12:45'}; %time
y=[0.5 0.8 0.3 0.6]                % values
time_out=datenum(x,'HH:MM');  %convert time to datenum

plot(time_out,y)              
datetick('x','HH:MM')         % show datetick on xaxis

[Samer Husam]

the values of x and y is not in array, so when i am using your answer i am getting an error, this what I am doing:

[num,T,vT] = xlsread(excle.xls,'Sheet1');      % reading excel
    x = num(:,1);                               % Time column
    y = num(:,4);                               % power column
    x1= datenum(x,'HH:MM');                     %convert time to datenum

    plot(x1,y)

but I am getting an error.. so how can I over come this??? and thanks for your answer

[Thomas]

what error are you getting and can you show how x is in MATLAB?

[Samer Husam]

the error i am getting is:

The input to DATENUM was not an array of strings.

[Thomas]

so what is your 'x'? Can you show an example of 'x' as it is imported in matlab. also what is the output of

whos x

[Samer Husam]

x is the time values to be read from excel (ex: 12:00 and 12:15)

y is the power values also to be read from excel.

Answer 2

[Samer Husam]

is it possible to use datetick function is this ?? please help...