Filter löschen
Filter löschen

Get mean and stdev from all values

3 Ansichten (letzte 30 Tage)
Dion Theunissen
Dion Theunissen am 3 Jun. 2021
Kommentiert: Steven Lord am 3 Jun. 2021
Hi,
I have a list like below. in the first column I have values from 0 to 91 (there can miss values).
0 3
0 4.50000000000000
0 1.37500000000000
0 5
0 3
0 0.838961038961039
0 2.80000000000000
1 1.50000000000000
1 0.555555555555556
1 1.71428571428571
1 3.38666666666667
1 4
1 3.38666666666667
2 1.73684210526316
2 1
2 1.30769230769231
2 2.73333333333333
2 1
2 2
I want to calculate the mean and standard deviation for all of these values if they exist.
How can I realise this? Now I have the folowing:
clear all; clc; close all;
standaard = readmatrix('/Users/diontheunissen/Documents/Apployee/Smart_driver/avgFuel.xlsx');
indices = find(standaard(:,1)==0);
standaard(indices,:) = [];
indices = find(standaard(:,2)>8);
standaard(indices,:) = [];
standaard(:,1) = round(standaard(:,1));
standaard = sortrows(standaard,1);
c = {};
for i = 0:5:85
if i == 0
lower = find(standaard(:,1) == i);
n = i+5;
upper = find(standaard(:,1) == n);
elseif i>1
lower = find(standaard(:,1) == i+1);
n = i+5;
upper = find(standaard(:,1) == n);
end
tab = standaard(lower(1):upper(end),:);
c{i+1} = tab;
end
referent2 = []
for j = 1:5:86
data = cell2mat(c(j));
referent(1,1) = data(1,1);
referent(1,2) = mean(data(:,2));
referent(1,3) = std(data(:,2));
referent2 = [referent2;referent]
end
snelheid = linspace(min(referent2(:,1)),max(referent2(:,1)));
a1 = interp1(referent2(:,1), referent2(:,2:end), snelheid, 'makima');
verbruik = a1(:,1);
upper = a1(:,1)+a1(:,2);
lower = a1(:,1)-a1(:,2);
figure
hold on
plot(snelheid, verbruik, '-b');
plot(snelheid, upper,'-r');
plot(snelheid, lower,'-g');
How can i change this script that i get the mean and stdev from all existing values?
thanks
  2 Kommentare
DGM
DGM am 3 Jun. 2021
Can you clarify the structure of the file and what you're trying to do? I'm assuming you're trying to find the blockwise mean and std for column 2, the blocks being described by column 1. Are all blocks the same size? Are the values in column 1 sorted?
Dion Theunissen
Dion Theunissen am 3 Jun. 2021
Indeed, the blocks have not the same size and are sorted in column 1.
So i need to check for each value from 1 untill 91 the mean and standard deviation

Melden Sie sich an, um zu kommentieren.

Akzeptierte Antwort

DGM
DGM am 3 Jun. 2021
Bearbeitet: DGM am 3 Jun. 2021
If column 1 is sorted:
% build test array
idx = repelem(1:10,randi(6,10,1));
idx = idx(1:20);
D = [idx.' rand(20,1)]; % the test array
% find length of blocks
blocklengths = diff([0 find(diff(idx)) numel(idx)]);
% split and process
C = mat2cell(D(:,2),blocklengths,1);
bkmean = cellfun(@mean,C)
bkmean = 6×1
0.8030 0.6236 0.4651 0.2942 0.4628 0.6299
bkstd = cellfun(@std,C)
bkstd = 6×1
0.1993 0.3422 0.1443 0.2592 0.5516 0.0849

Weitere Antworten (1)

Stephan
Stephan am 3 Jun. 2021
Bearbeitet: Stephan am 3 Jun. 2021
Use a table and then use findgroups combined with splitappy. This will allow you to solve the problem with a few lines of code. This will also work if the columns are not sorted.
  1 Kommentar
Steven Lord
Steven Lord am 3 Jun. 2021
findgroups can operate on numeric data as well as tabular data.
But rather than call those two functions sequentially, I'd probably just use groupsummary.
X = [0 3;
0 4.50000000000000;
0 1.37500000000000;
0 5;
0 3;
0 0.838961038961039;
0 2.80000000000000;
1 1.50000000000000;
1 0.555555555555556;
1 1.71428571428571;
1 3.38666666666667;
1 4;
1 3.38666666666667;
2 1.73684210526316;
2 1;
2 1.30769230769231;
2 2.73333333333333;
2 1;
2 2];
[M, BG] = groupsummary(X(:, 2), X(:, 1), @mean)
M = 3×1
2.9306 2.4239 1.6296
BG = 3×1
0 1 2
check = mean(X(X(:, 1)== 1, 2)) % This is the same as M(BG == 1)
check = 2.4239
S = groupsummary(X(:, 2), X(:, 1), @std)
S = 3×1
1.5037 1.3554 0.6728
MS = groupsummary(X(:, 2), X(:, 1), {@mean, @std}) % Compute M and S simultaneously
MS = 3×2
2.9306 1.5037 2.4239 1.3554 1.6296 0.6728

Melden Sie sich an, um zu kommentieren.

Kategorien

Mehr zu Numeric Types finden Sie in Help Center und File Exchange

Produkte


Version

R2021a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by