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

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Kasmita Devi il 21 Mag 2024 alle 7:20
Commentato: Steven Lord il 21 Mag 2024 alle 15:10
set(gca, 'YScale', 'log')
ylim ([0 1e-308])
Instead of 1e-308 i want 1e-2000. how can i set the limit plz
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### Risposta accettata

Hassaan il 21 Mag 2024 alle 8:35
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
-----------------------------------------------------------------------------------------------------------------------------------------------------
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Kasmita Devi il 21 Mag 2024 alle 9:05
Thank you so much sir . it is working.

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### Più risposte (1)

Walter Roberson il 21 Mag 2024 alle 7:33
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.
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Kasmita Devi il 21 Mag 2024 alle 7:56
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 il 21 Mag 2024 alle 15:10
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

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