A method includes displaying a chart. The chart includes a first set of data marks and a line that connects adjacent data marks. The method further includes detecting a first input at a location that corresponds to the chart and, while detecting the first input: horizontally expanding at least a portion of the chart; expanding at least a portion of the line; and adding a second set of data marks on the line, where each data mark is placed on the line based on its respective abscissa, independent of the respective ordinate. The method also includes, for each data mark placed at a vertical position distinct from its respective ordinate: (1) animatedly moving the data mark vertically in accordance with the respective ordinate and a vertical scale for the vertical axis; and (2) animatedly adjusting the line so that the line connects the second set of data marks.