docs: def limits(self,x1,x2,y1,y2):
          """Set the coordinate boundaries of plot"""
          import math
          self.x1=x1
          self.x2=x2
          self.y1=y1
          self.y2=y2
          self.xscale=(self.cx2-self.cx1)/(self.x2-self.x1)
          self.yscale=(self.cy2-self.cy1)/(self.y2-self.y1)
  
  	ra1=self.x1
  	ra2=self.x2
  	dec1=self.y1
  	dec2=self.y2
          (sx1,sy2)=self.p2c((ra1,dec1))
          (sx2,sy1)=self.p2c((ra2,dec2))
  	
          
          self.config(scrollregion=(sx1-self.lgutter,sy1+self.bgutter,sx2+self.rgutter,sy2-self.tgutter))