OptionalxNumeric x axis instead: data x of the grid's left / right edges
OptionalxColumn labels (categorical x axis; tick value = column index)
OptionalyNumeric y axis instead: data y of the grid's bottom / top edges
OptionalyRow labels (categorical y axis; tick value = row index)
Row-major
cols x rowsvalues (values[row * cols + col]); NaN = empty cell. Up to 4096 x 4096.