The current model is assumed to be M1 (A1 + A2 + A3 + A4 + M2 (A5) ), where the
Mx models are multiplicative and the Ax models are additive.
XSPEC> eqwidth 3 ! Calculate the total flux of component A2 (the third component of the model) and find its peak energy (E). The continuum flux is found by the integral flux of A1+A3+A4, using the range of 0.95 * E to 1.05 * E to estimate the flux.
XSPEC> eqwidth range .1 ! As before, but now the continuum is estimated from its behavior over the range 0.9 * E to 1.1 * E.
XSPEC> eqwidth range 0 ! Now the continuum at the single energy range (E) will be used.
XSPEC> eqwidth range .05 2 ! Now the component A1 is used as the feature, and A2+A3+A4 are used for the continuum. The range has been reset to the original value.
XSPEC> eqwidth 1 ! Illegal, as M1 is not an additive component.
XSPEC> eqwidth 7 ! Illegal, as there is no other additive component with A5 in its group to be used as the continuum.