how change calm series axis

i am controlling cgcontextshowtext arrangement text, nonetheless rotating controlling cgaffinetransformation, series focus located during left, during core drawn text, formula i am controlling this:

cgcontextsavegstate(context);

cgcontextselectfont(context, "helvetica", 20, kcgencodingmacroman);
cgcontextsetcharacterspacing (context, 1);
cgcontextsetrgbfillcolor (context, 0, 0, 0, 1);
cgaffinetransform xform = cgaffinetransformmake(
    sin(degreestoradians(angle)), cos(degreestoradians(angle)),
    cos(degreestoradians(angle)), -sin(degreestoradians(angle)),
    0,  0);

cgcontextsettextdrawingmode (context, kcgtextfill); 

cgpoint degreedisplaypoint = cgpointmake(100,100);
cgcontextshowtextatpoint(context, degreedisplaypoint.x, degreedisplaypoint.y, [anglestringwithdegree cstringusingencoding:nsmacosromanstringencoding], [anglestringwithdegree length]); 

cgcontextrestoregstate(context);

any ideas?