curve distorted with time

Hello all I am trying to plot data from the attached test.mat file. If I just plot the data alone using the command plot(raw_summer_0mean), I got a nice curve shown below, but when I plot it with the time(attached below) , the curve is distorted. Any suggestions. Thanks in advance.

raw_summer_0mean=raw_summer-mean(raw_summer);

figure;plot(x_data_summer,raw_summer_0mean)
line([1 length(raw_summer_0mean)],[std(raw_summer_0mean) std(raw_summer_0mean)],'Color','r','LineWidth',1,'LineStyle','--')
line([1 length(raw_summer_0mean)],-[std(raw_summer_0mean) std(raw_summer_0mean)],'Color','r','LineWidth',1,'LineStyle','--')
text(x_data_summer(3),std(raw_summer_0mean)+1,['\sigma ',num2str(std(raw_summer_0mean))])
xlabel('Time')
ylabel('Precipitation Raw')

axis([min(x_data_summer)  max(x_data_summer)   min(raw_summer_0mean) max(raw_summer_0mean) ])
set(gca,'XTick',x_data_summer(1):diff(x_data_summer):x_data_summer(length(x_data_summer)))
datetick('x','yyyymmm','keeplimits', 'keepticks')
rotateXlabels(gca,90)

[Star Strider]

Suggestions to do what?

[ahmed shaaban]

The two curves suppose to be identical, I need suggestions to have get the same curve when I put time on x axes.

Answer 1

[Chad Greene]

Your time vector x_data_summer is not evenly spaced. When you only plot the raw_summer_0mean data, Matlab is assuming the x axis is evenly spaced. But your date numbers skip the winters.

[Chad Greene]

You don't have data in the winter, so when you reference your raw_summer_0mean data to its corresponding dates, Matlab will connect the last summer measurement of one year to the first summer measurement of the next year with a straight line.

[Chad Greene]

[ahmed shaaban]

ya, that is right, the data is only for June, July, august, September. Is there is any way to just enforce matlab to plot only the selected months without making such connections.

[Chad Greene]

You mean like this?

[y,m,d] = datevec(x_data_summer); 

for k = y(1):y(end) 
    plot(x_data_summer(y==k),raw_summer_0mean(y==k),'b*-'); 
    hold on;
end
datetick

[ahmed shaaban]

Yes,I try that and it give me the following figure. is there a way that I can enforce the datetick to be only in summer (July for example). The datetick here vary between all months Thanks alot

re. Thanks a lot.