The last challenge created and appended a rectangle to the `svg` element for each point in `dataset` to represent a bar. Unfortunately, they were all stacked on top of each other.
The placement of a rectangle is handled by the `x` and `y` attributes. They tell D3 where to start drawing the shape in the `svg` area. The last challenge set them each to 0, so every bar was placed in the upper-left corner.
For a bar chart, all of the bars should sit on the same vertical level, which means the `y` value stays the same (at 0) for all bars. The `x` value, however, needs to change as you add new bars. Remember that larger `x` values push items farther to the right. As you go through the array elements in `dataset`, the x value should increase.
The `attr()` method in D3 accepts a callback function to dynamically set that attribute. The callback function takes two arguments, one for the data point itself (usually `d`) and one for the index of the data point in the array. The second argument for the index is optional. Here's the format:
It's important to note that you do NOT need to write a `for` loop or use `forEach()` to iterate over the items in the data set. Recall that the `data()` method parses the data set, and any method that's chained after `data()` is run once for each item in the data set.
# --instructions--
Change the `x` attribute callback function so it returns the index times 30.
**Note**
Each bar has a width of 25, so increasing each `x` value by 30 adds some space between the bars. Any value greater than 25 would work in this example.
