Denny's D3 practice

I generate 50 object having x and y attributes with
Math.random()
, and using the technique we've learned from previous lessons to visualize it to respond points
Then use
d3.svg.axis()
to generate the axis, notice that it won't show up on the screen now since we haven't appended it on the canvas.
And we append a group element(
g
stands for "group"), put our axes into it.
Boom!
The awful-look axis is created.
Needs some styling on it(Hint: Maybe we just remove the "fill" attribute will make thing alright.)
About the shape-rendering attribute of svg, refering this posthelps me a lot.
The below is optional method in
axis()
.
1. tickPadding()
  is the padding between the tick-text and axis.
2. tickValues([min, max])
  can adjust the tick range while we don't satisfy what d3 automaticaly generate for us.
  It sounds we can do something like this to marked each element in data:
  
  tickValues(data.map(function(d){ return d;}))
  
  (Apparently not a good choice in this case.)