'Hold on' not working for pcolor graph?

Hello. I have calculated an average mean temperature for a given time and height. The sequence follows through eleven different data sets, and I have used pcolor to graph them. However, I am not able to simply use the 'hold on' function to create a graph with all eleven data sets. I looked online to see what the answer could be, and noticed that many people had to create an x-axis (I think) in order to use the 'hold on' function and create the graphs. After a few attempts on my own, I have been very unsuccessful at doing this. Can anyone give me examples on how I would set my axes and use pcolor to create a graph?

I tried:

ax1=(110600:500:142600);
figure(1)
pcolor(x1,y1,temp1);
hold(ax1,'on')
pcolor(x2,y2,temp2);
pcolor(x3,y3,temp3);
pcolor(x4,y4,temp4);
pcolor(x5,y5,temp5);
pcolor(x6,y6,temp6);
pcolor(x7,y7,temp7);
pcolor(x8,y8,temp8);
pcolor(x9,y9,temp9);
pcolor(x10,y10,temp10);
pcolor(x11,y11,temp11);
hold off

I am trying to set my x-axis to a incremental time that includes all 11 data sets, but MATLAB did not recognize the format 'hold(ax1,'on')'. Thank you in advance.

Answer 1

[Ameer Hamza]

You are using the hold command wrong. The first input to hold must be an axis object. Use it like this

figure(1)
p = pcolor(x1,y1,temp1);
hold(p.Parent,'on')

the subsequent calls to pcolor() will plotted on the same axis.

[Wafa'a Shanti]

The same problem is arising- it is only plotting the first graph. I think why I tried to set my axes is because every x-value in about a 5 minute increment in time, so the first plot will not suffice as the main axis. Can I set my axis to accommodate every plot? That is why I tried to set my x-axis manually, but may have not done it correctly.

[Ameer Hamza]

Can you share your sample data? It will be easy to find the issue.

[Wafa'a Shanti]

ftime11=cellstr(datestr(time11)); %creates time as a number
ftime11=split(ftime11);
ftime11=ftime11(:,2);
ftime11=cell2mat(ftime11);
ftime11=cellstr(ftime11);
ftime11=strrep(ftime11,':','');
ftime11=char(ftime11);
ftime11=str2num(ftime11);
lower = 0;
index=1;
tlower=142900;
m11=zeros(20,1);
for tupper=143400:500:143900 %between certain time, find temps associated with the time and height
  for upper=10:10:100
      m11(index)=mean(T11(find((ftime11>tlower & ftime11<=tupper) & ((z11>lower &z11<=upper)))));
      index=index+1;
      lower=upper;
  end
  tlower=tupper;
end
t1k=m11(1:10,1); %create arrays for values based on given time increments
t2k=m11(11:20,1);
temp11=[t1k t2k];
Ts11=[142100 142600]; %set time array
Zs11=[5:10:95]; %set height array
[x11,y11]=meshgrid(Ts11,Zs11); %mesh time and height for graphing temperature associated with given time and height.

The main purpose is to create a heatmap at a given height and time. There are 11 different data sets (this is the last one). The time increments as follows: 110600:500:142600. What changes for each code is the increment of time- most have 3 sets of arrays created for values based on given time increments, one has 4 sets, and the last two data sets have 2 sets, if this makes sense.

[Steven Lord]

Do the axes limits at the time you called hold on encompass the range of the X data you use in your pcolor calls? Holding the axes allows you to plot multiple graphics objects on the axes and freezes the axes limits. So if your X axes limits were from 0 to 1 and you tried to plot something from X = 2 to X = 3, it would be plotted but you wouldn't see it. If that's the case, you may want to use the xlim function to adjust the limits on the axes.

[Wafa'a Shanti]

Thank you so much for your help. This gives me the correct axis, but it does not show me the varying temperatures. Except a slab at the very end showing the start of the second pcolor-line, the graph is mainly of the first pcolor-line. Extending the axis unfortunately does nothing (I was hoping it would).

[Image Analyst]

Your code does not run because time11 is not defined. What is it???? Like Ameer asked, please attach your data plus code to read it in.

[Wafa'a Shanti]

I did not realize he wanted the whole code, sorry for that. t_11.725 is one data set. Since the data sets are all the same, I do not think you need all 11 attached. Columns are as follows: height, u-component wind, v-comp wind, T, ignore the next three, Time. (the other columns are not necessary).

[Ameer Hamza]

@Wafa'a, Although I am not able to run your complete code but based on what you said if you just want to animate the variation in the graph, then a simple solution is to not hold the axis and insert a pause between two consecutive plotting statements. For example, try this

pcolor(x1,y1,temp1);
pause(1);
pcolor(x2,y2,temp2);
pause(1);
pcolor(x3,y3,temp3);
pause(1);
% and so on

[Wafa'a Shanti]

Thank you for this, and it will act in the place needed until I can figure this out. However, my desire is to have every line plotted on one graph. Is it possible that the use of meshgrid is wrong? If every data set has a meshgrid solely for its' data set, would p-color be able to adapt to the new meshgrid and plot the next p-color line?

[Ameer Hamza]

Yes, it is possible to plot everything one one figure window. But to suggest you the correct way, we need to have the dataset you are using to plot. Because right now it is difficult to know how the xlimits and ylimits of the data are changing. Also please only attach a .mat file with variables x1,y1,temp1, x2,y2,temp2, ... Attaching the whole script also make the spotting of error difficult.

[Wafa'a Shanti]

There are the first two data sets, and the updated code. I appreciate your help and patience.

[Ameer Hamza]

Are you looking for something like this?

figure(1)
p = pcolor(x1,y1,temp1);
hold(p.Parent)
pcolor(x2,y2,temp2);
xlim([x1(1) x2(end)])

replace x2(end) with the x11(end) in the last line.

[Wafa'a Shanti]

Yes, this is what I am looking for. However, it does not plot the correct temperatures as I add more pcolor-lines. Is there a way to fix this?

[Ameer Hamza]

How do decide it is not correct? The color depends on the matrix temp1, the color map p.Parent.Colormap and the value of p.Parent.CLim. Attach an image showing why do you think that the color is incorrect. It is easier to suggest an alternative if you provide complete detail of your problem.

[Wafa'a Shanti]

Disregard that comment please. The color scheme on an individual plot is much different compared to when plotting everything at once. Thank you so much for your help. If I have further questions, can I please comment on here for them to be answered, or should I start a new thread?

[Ameer Hamza]

If it is related to the question, i.e. pcolor() and hold() then you are welcome to comment here. If it is different then it is better to start a new question.

Answer 2

[Jan René Haak]

I have almost the same problem. However, I have a matrix S that I want to plot using pcolor. So far, no problem. But the matrix S is calculated in a loop and changes every iteration. Is there a possibility, just like hold on for normal plotting, to plot S every iteration?