## 3.9.1 Horizontally arranged data files

Pyxplot also allows rows of data to be plotted against one another. To do so, the keyword `rows` is placed after the `using` modifier:

    plot 'data.dat' index 1 using rows 1:2

For completeness, the syntax `using` `columns` is also accepted, specifying that columns should be plotted against one another, as happens by default:

    plot 'data.dat' index 1 using columns 1:2

When plotting horizontally-arranged data files, the meanings of the `index` and `every` modifiers are altered slightly. The former continues to refer to vertically-displaced blocks of data separated by two blank lines. Blocks, as referenced in the `every` modifier, likewise continue to refer to vertically-displaced blocks of data points, separated by single blank lines. The row numbers passed to the `using` modifier are counted from the top of the current block.

However, the line numbers specified in the `every` modifier – i.e. variables , and in the system introduced in the previous section – now refer to vertical column numbers. For example,

    plot 'data.dat' using rows 1:2 every 2::3::9

would plot the data in row 2 against that in row 1, using only the values in every other column, between columns 3 and 9.