logistic regression compare with scikit

i use simple (x,y,label) data for viewlize decision bound. at the first glance, the effect is not satisfied. i find the reason is that: 1 do not add constant 1; 2 need updata all error and weight simultaneous. after i revise that, better but not perfect. so i compare with scikit, i find the effect of scikit is just so so too.
one thing i can not understant: when plot bound line, the constant item for scikit is - while for mine is +.