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Charts with horizontal category axes

 

Charts with horizontal category axes (short: horizontal charts) typically display time series. Use the horizontal category axis as a time axis. Vertically, the visualization elements represent the data per time period or point of time (there is no need to show a vertical value axis as the visualization elements carry their own values). Time category axes run from left to right and show characteristics of period types (e.g. months or years) or points of time (dates).

In general, the data series of a horizontal chart is represented by columns (single, stacked, grouped), vertical pins, horizontal waterfalls, or lines. Vertical pins can be considered very thin columns. Because of their importance for the IBCS, they are dealt with in a separate section.

Here follows the grouping of horizontal chart types:
 

Single column charts

In general, single column charts (short: single columns) are used to display the temporal evolvement of one data series.

 

Single columns consist of:

  • Horizontal category axis: The horizontal category axis represents with its labels the respective time periods or points of time. The IBCS part on "Semantic rules" suggests to use the category width (see width A in the figure on the left) for identifying the period type (see the UNIFY rule UN 3.3 "Unify time periods"). 
  • Columns: One column per time period or point of time extends from the category axis in accordance with the respective value. Columns are displayed in the foreground of the category axis, so that the length of the column is not hidden. The IBCS part on "Semantic rules" suggests that the ratio of column width to category width (see ratio B/A in the figure on the left side) represents information about the measure type (see the UNIFY rule UN 3.1 "Unify measures").
  • Legends: As there is only one data series, the legend (name of the data series) is part of the chart title.
  • Data labels: Data labels name the values of the data series corresponding to the length of the respective columns. Position the labels of positive values above their respective columns, the labels of negative values below.
 

Stacked column charts

Stacked column charts (short: stacked columns) represent more than one data series (e.g. multiple products, countries, or divisions).

 

Stacked columns consist of:

  • Horizontal category axis: See single column charts.
  • Columns: The columns (see single column charts) are divided into segments (Excel names them “data points”) representing the data series (stacked columns).
  • Legends: Legends (names of the data series) are positioned either on the far left side with right-aligned text or on the far right side with left-aligned text. The column segments define their vertical position, centered vertically with the data labels of the respective column segment. If a segment at the far left or far right is missing or has a very small size, its legends might need assisting lines.
  • Data labels: Data labels name the values of the data series corresponding to the length of the respective column segments. If the sum of the column segments of a category is positive (column pointing upward), the label of the sum is positioned above the respective column, if negative (column pointing downward), it is positioned below.

It must be pointed out that stacked columns should only be used if all chart values are either positive or negative.


If the values of all segments vary greatly, stacked columns might not be the best choice. Position the data series of central importance or interest directly on the axis in order to best see its development over time.

 

Grouped column charts

Grouped column charts (short: grouped columns) show, in general, time series for a primary scenario (e.g. AC or FC) in comparison with a reference scenario (e.g. PY or PL). Two columns per category (grouped columns) represent these two scenarios.

 

The columns of the primary scenario and the reference scenario overlap, the reference scenario placed behind the primary scenario – either to the left or right of the primary scenario (see figure here on the left side as well as the paragraph on "Scenario comparisons" in the UNIFY rule UN 4.1 "Unify scenario analyses").

 

A third scenario could be displayed using a reference scenario triangle. All other elements of a grouped column chart are identical to single column charts.

   
 

Instead of using grouped columns, the primary scenario can be represented with a single column with the reference scenario represented by reference scenario triangles (see top chart of figure here on the left).

 

Horizontal pin charts

Horizontal pin charts (short: horizontal pins) are used for the visualization of relative variances in a time series analysis.

 

Horizontal pins consist of:

  • Horizontal category axis: see single column chart.
  • Pins: One pin per time period or point of time extends from the category axis to the respective length. The pin has the size of a very thin column. Color the pin green or red corresponding with positive or negative relative variances respectively. The fill of the pinhead represents the primary scenario (see the paragraph on "Scenario comparisons" in the UNIFY rule UN 4.1 "Unify scenario analyses". Display the pins in the foreground, so that the length of the pin (see length X in the figure on the left side) is not hidden.
  • Legends: As there is only one data series, the legend (name of the data series) is part of the chart title.
  • Data labels: Data labels name the values of the data series consistent with the length of the respective pins. Position the labels of positive values above the respective pins, labels of negative values below.
 
 

Horizontal waterfall charts

Horizontal waterfall charts (short: horizontal waterfalls or column waterfalls) analyze root causes, over time, for the change or variance between two or more statuses. Accordingly, horizontal waterfalls consist of two or more status columns. In between the status columns are contribution columns demonstrating what led to the difference between two status columns.

 

Horizontal waterfalls start with an initial status column and end with a final status column. In between are contribution columns, which start at the end value, i.e. the height, of the preceding column, and show the positive or negative contribution as well as the accumulated contribution of all columns up to the respective point of time.

 

There are two types of horizontal waterfalls:

   

Growth waterfalls: In growth waterfalls the status columns represent a stock measure (e.g. headcount, accounts receivable) at different points in time (e.g. end of Q4 2012, 2013 and 2014). The contribution columns in between represent the changes (increases and decreases) over time of this stock measure.

 

(There is no vertical equivalent to the horizontal growth waterfall.)

   

Horizontal variance waterfalls: In horizontal variance waterfalls the status columns represent a flow measure (e.g. sales) at different periods in time (e.g. 2013 and 2014) and/or regarding different scenarios (e.g. PL and AC). The contribution columns in between represent the periodical variances between the different time periods and/or scenarios.

 

The elements of a horizontal waterfall chart are the same as the elements of single column charts. In addition, assisting lines connect the beginning of a status or contribution column to the end of the preceding column.

 

 

 

Line charts

In general, line charts are used for the display of the temporal evolvement of data series with many data points.

 

Many data points lead to small category widths. The advantage of line charts over column charts is the simplified display of data (better data-ink-ratio [1] ). In addition, they can better represent positive and negative values of more than one data series than columns. On the other hand, lines tend to imply a continuous timeline – practically non-existent in business communication. Therefore lines should not be used for the presentation of data series with only a few values.

 

Line charts cannot be “stacked” in order to show structure like in stacked column charts. In the place of line charts for “stacked data”, area charts offer a good solution (there is no layout concept for area charts in this version of IBCS yet).

 

Line charts with more than three intersecting lines tend to be confusing. Instead, several smaller charts with one line each could be placed next to one another (small multiples), particularly when the general trends of the lines are to be analyzed – not the direct comparison of two data series (e.g. in comparing seasonal developments of several years).

 

Line charts consist of:

  • Horizontal category axis: See single column chart. The semantic rules in part 3 of the IBCS Standards suggest to use the category width (see width A in the figure on the left) for identifying the period type (see the UNIFY rule UN 3.3 "Unify time periods").
  • Lines: One or more lines with line markers represent the values of the respective data series. Use line thickness, line color, and line markers for meaning, see part "Semantic rules").
  • Legends: Legends label the data series. If the line chart shows only one data series, include the legend in the chart title. If the line chart shows two or more data series, the legend should be positioned to the right of the far right data point (left-aligned text) or the left of the far left data point (right-aligned text). You can position legends also close to the lines at any other place in the chart.
  • Data labels: Data labels name the values of the respective data points. If possible, label maximum values (peaks) above the line markers and minimum values (valleys) below the line markers. In many practical applications it is not necessary to clutter the line chart by labeling every data point, see the SIMPLIFY rule SI 5.3 "Avoid unnecessary labels".
 
 

Other horizontal charts

Other chart types with horizontal category axes are boxplot charts (range charts) and area charts. There is no specific notation concept for these chart types yet however it can be easily derived from the notation concept of column and line charts.

 
 

[1] The data-ink ratio is defined as the proportion of graphic’s ink devoted to the non-redundant display of data-information, see Tufte, Edward: The Visual Display of Quantitative Information”, second edition, March 2011, page 93

 

 

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