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Hi, I plotted a cumulative sum in Matlab. Is there any where for me to get the value of x from the plot(value of y is known)?
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x never equals 7000. Not sure which bar graph you were looking at but none of them have an x value of 7000. Now if you want the x value where y first exceeds 7000, then you can look at the last few lines I tacked on to the bottom of their example (which is the top several lines):
clear clc; workspace; % Make sure the workspace panel is showing. format longg; format compact; fontSize = 20;
x = -2.9:0.1:2.9; y = randn(10000,1); figure(1) hist(y,x); xlabel('x', 'FontSize', fontSize); ylabel('y', 'FontSize', fontSize); title('Histogram', 'FontSize', fontSize);
% Calculate number of elements in each bin n_elements = histc(y,x); % Calculate the cumulative sum of these elements using cumsum c_elements = cumsum(n_elements) % Plot the cumulative distribution like a histogram using bar: figure(2) bar(x,c_elements,'BarWidth',1); grid on; % Enlarge figure to full screen. set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Find out x when c_elements = 7000 % first find the index. x7000Index = find(c_elements >= 7000, 1, 'first') % Then find the x value for that index. x7000 = x(x7000Index); message = sprintf('The cumulative sum first exceeds 7000\nat an x value of %.1f', x7000); uiwait(msgbox(message));
It depends on what you exactly want...
Actually the X-values are trivial:
data = rand(1, 100); y = cumsum(data); lineH = plot(y); % Now the X-values are: x = 1:numel(y); % You can obtain them explicitly: x2 = get(lineH, 'XData');
Thank you for your reply. Actualy I did the cumsum from this example: http://www.mathworks.co.uk/help/matlab/ref/histc.html
According to the bar graph, I need to find the y value when x=7000.