After the overview provided by parallel histograms, 2D graphs let you focus on 2 variables, placed along the horizontal and vertical axes, and several other variables that you can assign to size or color. 2D graphs let you see more details on the precise correlations to be found between the 2 major variables.

The following view is obtained with 6 interactive parameter settings: we choose to assign an ellipse to each data object, set each ellipse's x coordinate to the Longitude attribute of the table, the y coordinate to the Latitude attribute, the width and height of each ellipse to the Population attribute, the color to the State attribute and the transparency of each ellipse is set to 1/3, so as to let small cities in densely urbanized areas still appear:

You should recognize the contours of the United States. This ability for you to recognize a known pattern is the key advantage of information visualization over other statistical knowledge discovery methods: the fact that you are seeing the United States is not known by the software, but only by you. When you discover other particularities in this data set, you will be able to orient or explain your findings according to knowledge that is not contained in the data set, but in your own knowledge.