On exit: the approximate derivative of the solution component
${y}_{i}$, as supplied in
${y}_{i}$ on output from the integration routine at the output value of
t. These values are obtained by the evaluation of
${y}^{\prime}=f(x,y)$ except when the output value of the argument
t in the call to the integration routine is
tout and
${\mathbf{tcurr}}\ne {\mathbf{tout}}$, in which case they are obtained by interpolation.