in y axis i want 10^(-2000). can anyone plz help

set(gca, 'YScale', 'log')

ylim ([0 1e-308])

Instead of 1e-308 i want 1e-2000. how can i set the limit plz

Answer 1

[Hassaan]

Assummed use case may help:

clc; clear all; close all;

% Generate dummy frequency data
f = linspace(0, 1000, 1000); % Frequency vector from 0 to 1000 Hz

% Generate dummy PSD data with very small values
PSD = 10.^(-2000 + randn(1, 1000) * 10); % Generate PSD data around 10^(-2000)

% Rescale the PSD to avoid numerical underflow
scale_factor = 10^2000;
rescaled_PSD = PSD * scale_factor;

% Plot the rescaled PSD
figure;
plot(f, rescaled_PSD);
title('Power Spectrum Density');
xlabel('Frequency (Hz)');
ylabel('Power/Frequency');
grid on;

% Set the y-axis to logarithmic scale
set(gca, 'YScale', 'log');

% Adjust y-axis tick labels to reflect the original scale
yticks = get(gca, 'YTick');  % Get current y-axis tick values
yticklabels = arrayfun(@(x) sprintf('10^{%d}', log10(x) - 2000), yticks, 'UniformOutput', false);
set(gca, 'YTickLabel', yticklabels);

% Set appropriate y-axis limits
ylim([10^-2000, 10^2]);  % Adjust according to the range of your data

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[Kasmita Devi]

Thank you so much sir . it is working.

Answer 2

[Walter Roberson]

1e-2000 would underflow to 0. You can only use such a number symbolically... but symbolic numbers cannot be used as limits.

You also cannot plot() such small numbers. I am not sure it is possible to fplot() them either.

Your best bet would be to rescale your numbers to something like 0 to 100 and then change your ytick labels to lie about the range.

[Kasmita Devi]

Thank you sir for your response. I know 1e-2000 is very small. but i need to show that in y axis. can it be possible by using vpa?

[Kasmita Devi]

Actually, I am getting my error 10^(-2000) which is very less and that is superior result as compared to existing results. so i want to plot that in y axis.

[Steven Lord]

You can show the text "1e-2000" on the axes.

plot(1, 1, 'o')
xticks(1)
xticklabels('1e-2000')

But as Walter stated, you cannot represent 1e-2000 as a double precision number. It underflows to 0. If you can't represent it as a double precision number, you can't plot it.

x = 1e-2000 % underflow

x = 0

x == 0 % x is exactly, down to the last bit, zero

ans = logical
   1

figure
h = plot(x, 1, '+');

h.XData % exactly zero

ans = 0