;calculate ellipses for a0, a1... ;first, set up a 2-d grid of values containing guessed values of dela0, dela1... dela0 = findgen(200) - 100. dela1 = 0.1*( findgen(200) - 100.) a0 = 96.625 + dela0 a1 = 4.50 + dela1 a0 = 0.1* dela0 a1 = 0.1* dela1 a0 = dela0 a1 = dela1 a0grid = fltarr( 200,200) a1grid = fltarr( 200,200) delchi = fltarr( 200,200) for nr=0, 199 do a0grid[ *, nr] = a0 for nr=0, 199 do a1grid[ nr, *] = a1 for nr0 = 0, 199 do begin for nr1 = 0, 199 do begin avec = [ a0grid[ nr0, nr1], a1grid[ nr0, nr1], 0] delchi[ nr0, nr1] = avec ## ss ## transpose( avec) endfor endfor contour, delchi, dela0, dela1, levels=[0.5,1.0,1.5,2.0], $ xra=[-20,20],yra=[-3,3], /xsty, /ysty end