How to plot a filled contour on a map plot?

Question

Alan Garger 2023-12-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2063502-how-to-plot-a-filled-contour-on-a-map-plot

评论： Star Strider 2023-12-24

I'm working on a project where I need to plot a filled contour onto a map. Ideally, this contour plot would be partially transparent so that the map underneath can still be seen. I was previously having issues where matlab didn't like plotting the output from countourf onto a geomap, so I implemented the solution found here:

https://www.mathworks.com/matlabcentral/answers/784501-how-to-combine-geoaxes-and-contourf-plot

This, however, only gives the contour lines, and not the filled areas. I also tried using a mapplot, but I have other data that also needs to be on this figure and that didn't end up working.

Here is the function I used, getContourLineCoordinates:

https://www.mathworks.com/matlabcentral/fileexchange/74010-getcontourlinecoordinates

and here is my current code:

geoscatter(points,"y","x","filled","MarkerFaceColor","#0000ff")

for m=1:length(shapes)

geoplot(shapes(m))

end

%plotting contour map from previous calculation

contdata = contourc(xrange,yrange,Ftotnorm',100);

cTbl = getContourLineCoordinates(contdata); % from the file exchange

% Plot contour lines

hold(ax,'on')

nContours = max(cTbl.Group);

colors = autumn(nContours);

for i = 1:nContours

gidx = cTbl.Group == i;

geoplot(ax, cTbl.Y(gidx), cTbl.X(gidx),'Color', colors(i,:)); % note: x & y switched

end

% Add colorbar

colormap("autumn")

colorbar(ax)

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Alan Garger 2023-12-23

Sorry about that, but I've attached the data. Points might have a different name than what I put in this code here.

Star Strider 2023-12-24

I delete my unaccepted answers. You don’t seem to have used my solution anyway.

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Answer 1

Alan Garger 2023-12-24

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2063502-how-to-plot-a-filled-contour-on-a-map-plot#answer_1376942

在 MATLAB Online 中打开

Alright after seeing the comment from Star Strider I realized that I needed to take a different approach rather than just trying to plot the contour data straight onto the map. What I did instead was to read the points from each layer and then plot each layer as a separate geopolyshape, similar to how the solution I mentioned in the original question plotted the contour lines onto the map.

figure()

ax = geoaxes();

geobasemap('satellite')

%plotting contour map from calculation

%calculating contour data

contdata = contourc(xrange,yrange,Ftotnorm',100);

Unrecognized function or variable 'xrange'.

cTbl = getContourLineCoordinates(contdata); % from the file exchange

hold(ax,'on')

nContours = max(cTbl.Group);

%finding every unique level

ltable=cTbl.Level;

levs=unique(ltable);

gpart=[];

%for loop that splits countour data into groups and adds a NaN after every

%group, then recombines the data. NaNs are added to be able to plot shapes

%with holes

for i=1:nContours

temp=cTbl(cTbl.Group==i,[1,3,4]);

temp=temp{:,:};

temp=[temp;temp(1,1),NaN,NaN];

gpart=[gpart;temp];

end

%converts the data into a table for a search in the next for loop

gpart=array2table(gpart,'VariableNames',["Level","Long","Lat"]);

%creates a cell array that will be useful later

lpart=cell(length(levs),1);

%for loop that separates groups by their layer, ie, its value for the

%"Z" axis

for i=1:length(levs)

temp=gpart(gpart.Level==levs(i),:);

temp=temp{:,:};

lpart(i)=mat2cell(temp,height(temp),3);

end

%color array that will be used to color the contour. Change "autumn" to

%change color gradient used

colors = autumn(length(lpart));

%for loop to actually plot the contour

for i=1:length(lpart)

%coordinates of the ith layer

shapemat1=cell2mat(lpart(i));

%coordinates of the next layer up, if statement for if there is no next

%layer

if i==length(lpart)

shapemat2=[];

else

shapemat2=cell2mat(lpart(i+1));

end

%combines this layer with the next layer

shapemat=[shapemat1;shapemat2];

%plots the shape from above. By combining the ith layer with the i+1

%layer, the ith layer get plotted and then the i+1 layer is then taken

%out. This is why I did the NaN stuff from before, to split the data up

%into something geopolyshape can recognize.

cshape=geopolyshape(shapemat(:,3),shapemat(:,2));

%actually plots the shape onto the map. alpha values are transparency

geoplot(cshape,'FaceColor',colors(i,:),'FaceAlpha',.25,'EdgeAlpha',.5)

end

geolimits([40.4,41], [-75.9,-75]);

% Add colorbar

colormap("autumn")

colorbar(ax)

Granted, this code still depends on the use of getContourLineCoordinates which can be found here. I tried uploading cTbl so that it can output here but it didn't want to upload. Trust me though, it worked. This method is also likely very ineffiecient and unoptimized, but hey, it works. Feel free to make it better if you so please

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How to plot a filled contour on a map plot?

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How to plot a filled contour on a map plot?

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