function [T,X] = expliciteuler(f, times, initial_value, stepsize)
% is used mostly like ode45, except for the missing options and additional
% stepsize parameter
T=[times(1):stepsize:times(2)];
X=zeros(length(initial_value(:)), length(T));
X(:,1)=initial_value(:);
for k=1:length(T)-1
    dx = stepsize.*  f(T(k), X(:,k));
    X(:,k+1) =  X(:,k) + dx(:);
end
X=X';