Examples:

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.