how can I change my time so that it takes frequency 1/250 hz

clc
clear all
close all

C = readtable('G2_adolescent.txt', 'NumHeaderLines',8);
%Convert to SI Units
accG2test = C{:,1}.*9.81;
forceG2test = C{:,2}.*0.00981;
dispG2test = C{:,3}./1000;
% time = dispG2test./accG2test;
forceG2test2 = smoothdata(forceG2test, 'sgolay', 100);
% Valleys Of Smoothed Data
[Vlys,vlocs] = findpeaks(-forceG2test2, 'MinPeakProminence',0.5);   
Vlys = [-forceG2test2(1); Vlys];
vlocs = [1;vlocs];
% Sampling Interval
Ts = 1;                                                             
t = 1:height(C);
figure
plot(t, forceG2test2)
hold on
plot(t(vlocs), -Vlys, '+r')
hold off


for k = 1:numel(vlocs)-1
	% Index Range For This Segment
    idx{k} = vlocs(k):vlocs(k+1);                                   
		% Time Vector
    tc{k} = t(idx{k});                                              
		% Signal Segment
    sc{k} = forceG2test(idx{k});                                    
end
 % Maximum Segment Length
tcmax = max(cellfun(@numel,tc));                                   
% Preallocate
ensb = zeros(tcmax,numel(idx));                                     
for k = 1:numel(idx)
	% Create 'Ensemble'
    ensb(1:numel(idx{k}),k) = sc{k};                                
end
figure
 % Plot Ensemble
plot(1:tcmax, ensb) 
title ('C:Force Vs Time (Cycles)');
legend('1','2','3','4','5','6','7','8','9');
xlabel('Time[sec]');
ylabel('Force[N]');

[Star Strider]

Missing: 'G2_adolescent.txt'

[Image Analyst]

I'm not sure what the question means "how can I change my time so that it takes frequency 1/250 hz". How does a time "take" a frequency? A frequency of (1/250) Hz means the period is 250 seconds. Do you want the x axis to go from 0 seconds to 250 seconds?

Answer 1

[Star Strider]

If is the sampling interval, multiply it by the sampling instants to convert them to time —

C = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/773388/G2_adolescent.txt', 'NumHeaderLines',8);
%Convert to SI Units
accG2test = C{:,1}.*9.81;
forceG2test = C{:,2}.*0.00981;
dispG2test = C{:,3}./1000;
% time = dispG2test./accG2test;
forceG2test2 = smoothdata(forceG2test, 'sgolay', 100);
% Valleys Of Smoothed Data
[Vlys,vlocs] = findpeaks(-forceG2test2, 'MinPeakProminence',0.5);   
Vlys = [-forceG2test2(1); Vlys];
vlocs = [1;vlocs];
% Sampling Interval
% Ts = 1;                                                             
Ts = 1/250;                                                                 % Define Sampling Interval
t = 1:height(C);
t = t * Ts;                                                                 % Multiply 't' By 'Ts' To Convert Samples To Time
figure
plot(t, forceG2test2)
hold on
plot(t(vlocs), -Vlys, '+r')
hold off

for k = 1:numel(vlocs)-1
    % Index Range For This Segment
    idx{k} = vlocs(k):vlocs(k+1);                                   
    % Time Vector
    tc{k} = t(idx{k});                                              
    % Signal Segment
    sc{k} = forceG2test(idx{k});                                    
end
% Maximum Segment Length
tcmax = max(cellfun(@numel,tc));                                   
% Preallocate
ensb = zeros(tcmax,numel(idx));                                     
for k = 1:numel(idx)
    % Create 'Ensemble'
    ensb(1:numel(idx{k}),k) = sc{k};                                
end
figure
% Plot Ensemble
plot(t(1:tcmax), ensb)                                                      % Subscript 't' To Show Time, Not Samples
% plot(1:tcmax, ensb) 
title ('C:Force Vs Time (Cycles)');
legend('1','2','3','4','5','6','7','8','9');
xlabel('Time[sec]');
ylabel('Force[N]');

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