fprintf into a stored variable
4 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
WhatIsMatlab-
le 12 Fév 2016
Commenté : per isakson
le 15 Fév 2016
Instead of using fprintf I want to store all the i, xe, and f(xe) into a vector instead. That way I can call them later. Also I had another problem where I wanted to use another 'i' later on in the code. But it only allowed me to use 1. How can you use two different 'i's. So they don't get mixed up.
f = @(x) x^2-6;
xl = 0;
xu = 10;
xe = (xu+xl)/(2);
acc = 0.00001;
while abs(f(xe))> acc
i = i + 1;
fprintf('%d)\t%f\tf(x)=%f\n',i,xe,f(xe));
if (f(xe)*f(xl)) < 0
xu = xe;
else
xl = xe;
end
xe = (xu+xl)/2;
end
0 commentaires
Réponse acceptée
per isakson
le 13 Fév 2016
Modifié(e) : per isakson
le 13 Fév 2016
Add
M = zeros( 0, 2 );
before the loop and replace
fprintf('%d)\t%f\tf(x)=%f\n',i,xe,f(xe));
by
M( end+1, 1:2 ) = [ xe, f(xe) ];
You'll get a warning about "Growing ..." , but if speed is acceptable ignore it.
 
"fprintf into a stored variable"   If understood literally, replace
fprintf('%d)\t%f\tf(x)=%f\n',i,xe,f(xe));
by
C{end+1,1} = sprintf('%d)\t%f\tf(x)=%f\n',i,xe,f(xe));
and add C=cell(0,1) before the loop
10 commentaires
per isakson
le 15 Fév 2016
- "but I got an error"   we cannot help if you don't show what you did and what error Matlab reported.
- "a better way of achieving this"   length(s) and length(m) tell the number of iterations in the two loops.
per isakson
le 15 Fév 2016
This example illustrates
- two ways to count the number of loop iterations
- two ways to store result in the loop
N = 1e6;
M1 = zeros( 0 );
ii = 0;
M2 = nan( N, 1 ); % Pre-allocate
while sqrt(ii) < sqrt(N) - 10
ii = ii + 1;
M1( end+1, 1 ) = ii;
M2(ii) = ii;
end
M2(isnan(M2)) = [];
disp( all( M2 == M1 ) )
disp( ii )
disp( length(M1) )
disp( length(M2) )
outputs
1
980100
980100
980100
where "1" shows that M1 and M2 are identical.
[Run and Time], i.e. the profiler, shows that "M1" is slower.
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Loops and Conditional Statements dans Help Center et File Exchange
Produits
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!