Determining Manual ROI from a graph (not image)

Hi Everyone,

I'm writing a matlab script to analyze some gait data I have. I currently have a graph that shows 5 distinct steps (below). I need to partition each step out to analyze separately, i.e. break it into 5 different variables.

I know in image processing there is a way to allow the user to input a region of interest to allow for further processing. My question is that is there a way to do this for non-images like graphs? If so, what would be the function to do this?

Thanks!

Jessi M.

Answer 1

[Image Analyst]

Sure, just use drawrectangle to drag out a box that defines the region you want to include.

% Demo to show how drawrectangle can be used to draw a rectangular box on the image, and crop out that rectangular region to a new image.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
y = rand(1, 50);
hFig = figure;
plot(y, 'b-');
hFig.WindowState = 'maximized';
% Ask user to draw rectangle.
button = 'Redraw';
while contains(button, 'Redraw', 'IgnoreCase',true)
    uiwait(helpdlg('Draw a box'));
    % User draws a box.  It exits as soon as they lift the mouse.
    hBox = drawrectangle('Color', 'r');
    
    % Get the coordinates in the form [xLeft, yTop, width, height].
    roiPosition = hBox.Position;
    % Delete the ROI object.
    delete(hBox);
    % and replace it with a rectangle in the graphical overlay.
    hold on;
    hRect = rectangle('Position', roiPosition, 'EdgeColor', 'r', 'LineWidth', 2);
    % Ask user if the rectangle is acceptable.
    message = sprintf('Is this good?');
    button = questdlg(message, message, 'Accept', 'Redraw', 'Reject and Quit', 'Accept');
    if contains(button, 'Quit','IgnoreCase',true)
        delete(hRect); % Delete the box from the overlay.
        roiPosition = [];
        break;
    elseif contains(button, 'Redraw','IgnoreCase',true)
        % OPTIONAL If you want to delete the prior one before drawing the next one.
        delete(hRect);
    elseif contains(button, 'Accept','IgnoreCase',true)
        break;
    end
end
% If you want to delete the rectangle from the overlay, do this:
delete(hRect); % Delete the box from the overlay.
% Show roiPosition in command window
roiPosition
xLeft = roiPosition(1)
yTop = roiPosition(2)
xRight = xLeft + roiPosition(3)
yBottom = yTop + roiPosition(4)
% Draw lines
xline(xLeft, 'Color', 'r', 'LineWidth', 2);
xline(xRight, 'Color', 'r', 'LineWidth', 2);
yline(yTop, 'Color', 'r', 'LineWidth', 2);
yline(yBottom, 'Color', 'r', 'LineWidth', 2);
caption = sprintf('xLeft = %.2f, xRight = %.2f.  yTop = %.2f, yBottom = %.2f', xLeft, xRight, yTop, yBottom);
title(caption, 'fontSize', fontSize)

If you want to turn the coordinates into indexes, you can use find() to find out which index is closest to the one you want. For example if you have x and y vectors

x1Index = find(x > xLeft, 1, 'first');
x2Index = find(x < xRight, 1, 'last');

Answer 2

[DGM]

That's what the data brush tool is for.

https://www.mathworks.com/help/matlab/ref/matlab.graphics.interaction.internal.brush.html

https://www.mathworks.com/help/matlab/creating_plots/interactively-explore-plotted-data.html#mw_e51f1358-ecba-48a9-a1cc-9749e1429e08