How do I plot different fields of a structure in a loop?

Hi all.

I'm very new to Matlab and I'm trying to create a loop that plots everything between these 2 lines of code:

scatter(MCR_full.MIB035.Reaches.R32.kin(:,1),MCR_full.MIB035.Reaches.R32.kin(:,3))
scatter(MCR_full.MIB035.Reaches.R42.kin(:,1),MCR_full.MIB035.Reaches.R42.kin(:,3))

so it would plot the following

scatter(MCR_full.MIB035.Reaches.R32.kin(:,1),MCR_full.MIB035.Reaches.R32.kin(:,3))
scatter(MCR_full.MIB035.Reaches.R33.kin(:,1),MCR_full.MIB035.Reaches.R33.kin(:,3))
scatter(MCR_full.MIB035.Reaches.R34.kin(:,1),MCR_full.MIB035.Reaches.R34.kin(:,3)) 

and so on all the way to

scatter(MCR_full.MIB035.Reaches.R42.kin(:,1),MCR_full.MIB035.Reaches.R42.kin(:,3)) 

all in the same plot. The RNN field name changes with each call to scatter.

Any help with this would be fantastic thanks so much

Answer 1

[Image Analyst]

Use dynamic field names:

% Create sample data
MCR_full.MIB035.Reaches.R32.kin = rand(100, 3)
MCR_full.MIB035.Reaches.R33.kin = rand(100, 3)
MCR_full.MIB035.Reaches.R34.kin = rand(100, 3)
MCR_full.MIB035.Reaches.R41.kin = rand(100, 3)
MCR_full.MIB035.Reaches.R42.kin = rand(100, 3)
% Get all the fieldnames.
fieldNames = fieldnames(MCR_full.MIB035.Reaches)
% Get data from each field and plot it.
for k = 1 : numel(fieldNames)
    thisFieldName = fieldNames{k};
    fprintf('Plotting %s.\n', thisFieldName);
    thisArray = MCR_full.MIB035.Reaches.(thisFieldName).kin;
    x = thisArray(:, 1);
    y = thisArray(:, 3);
    % Unique, random color for each.
    thisColor = rand(1, 3);
    % Do the scatter plot
    scatter(x, y, 30, thisColor, 'filled');
    hold on; % Don't let subsequent plots blow away earlier ones.
end
grid on;

[Josh Tome]

I'm looking to do something similar... in the above example, what if you only wanted to plot R33, R34, and R42 (a subset of the fields) of MCR_full.MIB035.Reaches?

I have a structure with many fields but only want to plot some of those fields in my for loop.

I would also like to plot over the previous field, but I suspect that is a matter of not using the hold on function.

[Image Analyst]

@Josh Tome, use ismember to get a list of those fieldnames which are in the list of ones you want to keep.

% Create sample data
MCR_full.MIB035.Reaches.R32.kin = rand(100, 3);
MCR_full.MIB035.Reaches.R33.kin = rand(100, 3);
MCR_full.MIB035.Reaches.R34.kin = rand(100, 3);
MCR_full.MIB035.Reaches.R41.kin = rand(100, 3);
MCR_full.MIB035.Reaches.R42.kin = rand(100, 3);
% Get all the fieldnames.
fieldNames = fieldnames(MCR_full.MIB035.Reaches);
fieldNamesToPlot = {'R33', 'R34', 'R42'};
indexesToKeep = ismember(fieldNames, fieldNamesToPlot)

indexesToKeep = 5×1 logical array
   0
   1
   1
   0
   1

fieldNames = fieldNames(indexesToKeep)

fieldNames = 3×1 cell array
    {'R33'}
    {'R34'}
    {'R42'}

% Get data from each field and plot it.
for k = 1 : numel(fieldNames)
    thisFieldName = fieldNames{k};;
    fprintf('Plotting %s.\n', thisFieldName);
    thisArray = MCR_full.MIB035.Reaches.(thisFieldName).kin;
    x = thisArray(:, 1);
    y = thisArray(:, 3);
    % Unique, random color for each.
    thisColor = rand(1, 3);
    % Do the scatter plot
    scatter(x, y, 30, thisColor, 'filled');
    hold on; % Don't let subsequent plots blow away earlier ones.
    legendStrings{k} = thisFieldName;
end

Plotting R33.
Plotting R34.
Plotting R42.

grid on;
legend(legendStrings)

[Image Analyst]

@Josh Tome not sure what "I would also like to plot over the previous field, but I suspect that is a matter of not using the hold on function." means. My code plots what you wanted to plot. If you don't have hold on, it will blow away everything and plot everything from scratch. If you have hold on it will add those data markers to the existing plot. Did you try the code in my last comment? If not, why not?