How to change the desired xaxis ticks and subsequent values in log log plot?

I have a flood frequency analysis data stored in a file named "Matlabdataforgraph.txt." My intention is to visualize this data using MATLAB. To achieve this, I have specified a set of desired tick marks for the x-axis, arranged in reverse order. Successfully incorporating these ticks into my MATLAB plot, I now seek to create a logarithmic scale for the y-axis. However, I am encountering an issue where the x-axis values from the text file are not aligning with the desired tick marks in the plot, resulting in a deviation from the anticipated straight line in the plot. I have provided the data, MATLAB code, and an image illustrating the expected curve for your reference. Thanks in advance

MATLAB CODE

Q = importdata('Matlabdataforgraph.txt');

T1= rmmissing(Q(:,3));

T2= rmmissing(Q(:,4));

T3= rmmissing(Q(:,5));

T4= rmmissing(Q(:,8));

figure;

semilogy(T1,T4,'or','linewidth', 1.5)

hold on

semilogy(T1,T2,'--k','linewidth', 1.5)

semilogy(T1,T3,'--b','linewidth', 1.5)

semilogy(Q(:,1), Q(:,2),'o','MarkerEdge',[0 0 0],'MarkerSize',8,'MarkerFaceColor',[.7 .7 .7]);

desiredTicks = [1 5 20 40 60 80 90 95 98 99.5]; % Set the desired tick positions

numTicks = numel(desiredTicks);

logTicks = logspace(log10(desiredTicks(1)), log10(desiredTicks(end)), numTicks);

set(gca, 'XTick', logTicks);

set(gca, 'XTickLabel', arrayfun(@num2str, desiredTicks, 'UniformOutput', false));

xlim([1, 100])

mappedDataX = interp1(logspace(log10(desiredTicks(1)), log10(desiredTicks(end)), numel(desiredTicks)), desiredTicks, T1);

% Interpolate values in T1 to find their equivalent positions in the original scale

interpValues_original_scale = interp1(desiredTicks, logTicks, T1, 'linear', 'extrap');

hold on

a1 = Q(:, 3);

a1 = a1(~isnan(a1));

b1 = Q(:, 4);

b1 = b1(~isnan(b1));

c1 = Q(:, 5);

c1 = c1(~isnan(c1));

legend({'50% confidence level','95% confidence level',' 5% confidence level','Gaged peak Q (Bulletin 17B)','PILF (LO)'},'Location','Northwest','fontsize',12)

legend boxoff

ylim([1,1000000]);

ax = gca;

ax.XScale = 'log';

ax.XDir = 'reverse';

xlabel('Annual Exceedance Probability (%)','fontweight','bold','fontsize',18);

ylabel('Annual Maximum Discharge (cumecs)','fontweight','bold','fontsize',18);

set(gca,'linewidth', 1.5,'fontsize',12,'fontname','Times New Roman')

grid on

gridColor = [0.7, 0.7, 0.7]; % Light gray color

set(gca, 'GridColor', gridColor);

set(gca, 'MinorGridColor', gridColor);

set(gca, 'GridLineStyle', '-');

set(gca, 'MinorGridLineStyle', '-');

gridLineWidth = 0.7;

set(gca, 'LineWidth', gridLineWidth);

saveas(gcf, 'sample_figure.png');

Answer 1

[Constantino Carlos Reyes-Aldasoro]

Hello

There are 2 separate properties that you have to handle, one is the ticks and the other is the ticklabels, and both are better managed if you use the handles effectively, for example

y=[ 0 1 2 9 6 5 9]; x = [1 2 3 4 5 6 7];
hAxis = gca;
hPlot = plot(x,y,'o');

If you do this in Matlab local, it will display a figure, here it will be displayed below.

Notice that I saved the handles of the axis and of the plot. Now we can modify the ticks and the labels.

hAxis.XTick = [1 1.5 2 3 5 6 11];
hAxis.YTickLabel{3}='three';

hAxis.YTickLabel{5}='F I V E';

In the lines above, I changed the values of xtick so that the ticks are placed in a certain location, not necessarily the same as the values of the data, and changed the values of yticklabel to anything you want.

I think if you use the properties, you will be able to fix your problem accordingly.