Probably because the Julia module has different default values for the absolute and relative tolerance. For Julia, the defaults are reltol=1e-5 and abstol=1e-8 but in Matlab the defaults are RelTol=1e-3 and AbsTol=1e-6.
https://github.com/JuliaLang/ODE.jl http://se.mathworks.com/help/matlab/ref/odeset.html That would also explain why the Julia program took so much longer. Try again with the same tolerance and see if the results are more similar. Oh, and like Erik said, you probably meant to have parenthesis around "1/8". If the results still look difference, look for more options that might have different default values. Cheers, Daniel. On Saturday, 11 June 2016 04:29:47 UTC+2, [email protected] wrote: > > this is the test for equation differential using runge-kutta45: f(x,y)= > (-5*x - y/5)^1/8 + 10 > > > <https://lh3.googleusercontent.com/-D6U4d5pN0pw/V1t3MaV3JpI/AAAAAAAAACU/-E_ceVhrTxkT3SAgmLUy5nHDhRJTIikSgCLcB/s1600/rk45.png> > > why the numerical result is different? I used : > > function Rk_JL() > f(x,y)= (-5*x - y/5)^1/8 + 10 > tspan = 0:0.001:n > y0 = [0.0, 1.0] > return ODE.ode45(f, y0,tspan);end > > > and > > > function [X1,Y1] = RK_M() > f = @(x,y) (-5*x - y/5)^1/8 + 10; > tspan = 0:0.001:n; > y0 = 1 > [X1,Y1]= ode45(f,tspan,1);end > >
