A method includes displaying at least a first portion of a chart at a first magnification, the first portion containing a plurality of data marks. The method also includes detecting a first input at a location that corresponds to the first portion of the chart and, in response, zooming in to display a second portion of the chart at a second magnification, the second portion including a first data mark in the plurality of data marks. The method further includes detecting a second touch input at a location that corresponds to the second portion of the chart, and, in response: if one or more predefined data-mark-information-display criteria are not met, zooming in to display a third portion of the chart at a third magnification, the third portion including the first data mark; and, if the one or more predefined data-mark-information-display criteria are met, displaying information about the first data mark.