Overview
Line charts use continuous lines to connect data points, making them ideal for visualizing trends, changes, or relationships over time or across sequential categories. Each line represents a series of data values plotted against an independent variable, which is typically a date field. This structure allows line charts to highlight patterns, fluctuations, and progressions across multiple data series simultaneously.
Because the margin sets the space between the chart axes and the edge of the container, ensure you add enough margin for any axis ticks or labels. If needed, use options in the Axes section such as Rotate Ticks to constrain the size of tick and label text.
Connecting to Datasets
In the
Dataset section, you can select the
dataset for your chart. If you need to add a dataset, this can be done by selecting
New Dataset in the
Project tab.
If you are on the Pro plan, you can upload your own files (in csv format) to use as datasets, by clicking New Dataset and then Upload Dataset.
After you have selected a dataset, you can optionally enable the Prefilter Dataset switch, which lets you filter the data that is supplied to the chart. The filter is a "prefilter" because it is applied before the visualization is generated; end users are unable to adjust the filter dynamically.
Next, the Data Format is displayed. You can select either Wide Data or Long Data. The data format should reflect the structure of the selected dataset. It also determines the fields that will need to be set for the chart.
Finally, choose the Fields that should be used to construct the chart:
- Horizontal Axis Field: The chart's independent variable, usually set to a date field. Any repeated values in this field are aggregated.
- Series Field (for wide data): The chart's dependent variables, which are number, percent, currency, or measurement fields used for each line series.
- Value Field (for long data): A numeric, percent, currency, or measurement field that serves as the chart's dependent variable. Each value in this field corresponds to a specific line series, defined by the Color Field (found in the Color section of the right panel).
Connecting to Filters
You can establish connections to filter elements under the Chart tab, in the Connections section, by making a selection under Filter.
A
Filter element can be styled as a series of checkboxes, a dropdown menu, or a slider. Values from the specified
Filter Field appear as individual checkboxes, dropdown menu items, or (for numeric filtering) slider values. A given chart can be connected to one or more filters, and the same filter can be connected to multiple charts or other elements.
When a filter element is connected to a chart, it dynamically controls the dataset records displayed in the chart based on the user's selections. Filters can also adjust the chart's axis range dynamically, provided one of the chart's axis fields is the same as the filter's Filter Field and the Minimum and Maximum Range values of that axis are set to auto.
Additionally, filter elements can inherit color formatting from a chart, provided that the chart is using
Long Data format and the chart's
Color Field is the same as the filter's
Filter Field. For more information, see the
Color Formatting section of the documentation for filter elements.
If your chart uses
Wide Data format, use a
Selector element instead of a filter to dynamically control the chart color series.
Typically, the
Filter element you connect to will use the same
Dataset as the chart element. However, this is not strictly necessary. If the filter and chart elements use different datasets, the filter will only affect the chart if the chart's dataset contains a field (column) with the same name as the
Filter Field in the filter element. In this case, the values in these fields must at least partially align for the filter to take effect. Any non-matching values between the fields will be ignored during filtering.
Connecting to Selectors
If you are using Wide Data format, you can establish a connection to a selector element under the Chart tab, in the Connections section, by making a selection under Selector.
Selector elements control which series fields are displayed in connected elements that use a wide data format. Selectors can be displayed as checkboxes, dropdowns, or legends. While a chart can be connected to only one selector, a single selector can be connected to multiple charts and other elements that use series fields. Once connected, the selector element dynamically controls the dataset fields (columns) passed to the chart as series fields based on user selections.
Sorting
You can choose whether to reverse the chart's horizontal axis under the Chart tab in the Sort section.
Axes
The Axes section of the Chart tab can be used to configure the Horizontal Axis and Vertical Axis respectively.
- Add Label: When enabled, label text appears adjacent to the axis. You can also align the label text.
- Customize Range: Specify a custom minimum and maximum value for this chart's vertical axis.
- Set Axis Line Location: When enabled, this option lets you control the position of the axis line. Auto places the axis line at the bottom of the chart (in the case of the horizontal axis) or the left of the chart (in the case of the vertical axis). Zero aligns the axis to the zero value and Hidden removes the axis line entirely. If this option is turned off, the chart's independent axis line will be displayed in a default location and the dependent axis line will be hidden (Pro users can adjust these default settings in the Theme page).
- Customize Ticks: When enabled, you can control which tick values will be displayed on the axis. Values lets you specify exact tick values, which should be separated with commas. Choose Count to set an approximate number of ticks (this option is only available on axes displaying continuous data). Or choose Hidden to remove ticks from the axis.
If you choose to specify exact tick values, ensure that they don't overlap with one another on tablet and mobile viewports.
- Rotate Ticks: On horizontal axes, you can rotate tick labels to angles of 0°, 30°, 45°, 60°, or 90°. This can improve readability, especially when dealing with long or overlapping tick labels.
- Use Short Format: On the dependent axis, you can display axis tick values in a compact format, such as 1K for 1,000 or 1M for 1,000,000.
The following chart formatting option applies to both axes:
- Clip Chart: Restrict the chart's lines and any annotations from extending beyond the boundaries of the chart container, ensuring all items remain within the outermost values on both axes.
Colors
Color formatting is defined in the Colors section under the Chart tab.
If the chart uses Wide Data format, separate colors can be assigned to each of the selected line series.
If the chart uses
Long Data format, you can specify a
Color Field, which can be a text field or numeric (number, currency, percent, or measurement) field from the selected dataset. If you select a text field, each unique value in that field will be treated as a series and can be assigned a color. For numeric fields, you can configure a
Color Gradient,
Domain Minimum and
Maximum, and
Color Scale. These features are explored in greater detail in our
Colors page.
Settings
In the Settings section under the Chart tab, specify the following options:
Curve: Choose how to interpolate the lines between points using various curve functions:
- "Linear" (the default) draws straight lines between points.
- "Bézier" draws a bézier curve with horizontal tangents between each point.
- "Monotone Cubic" draws a smooth cubic spline using Steffen's method. This is generally the optimal method of drawing curved lines because it maintains both smoothness and monotonicity.
- "Cardinal Cubic" creates flowing curves using a "cardinal spline", though with no guarantee of monotonicity.
- "Natural Cubic" creates the most "natural" spline, prioritizing smoothness and avoiding abrupt changes in curvature, with the most frequent violations of monotonicity.
- "Step After" and "Step Before" produce abrupt, stair-like changes either after or before each point.
The curve types available in Mappica can be tested below.
Range Fields
In line charts, it is possible to toggle on Add Range Fields, which draws ranges between two points (a "High value" and a "Low value") and associates each range with a line series on the chart. This is typically used to add visual context to the variability or uncertainty associated with a particular data series, through statistical measures such as confidence intervals and prediction intervals.
The range field is always assigned the color of the line series that it is associated with. You can choose the Opacity of the shaded ranges on the chart (with the default set to 30%).
If the chart uses Wide Data format, you will need to specify separate dataset fields (columns) for the high and low range values for each line series. For example, assuming series "A" and "B" are added as lines in the dataset, you will need to select columns "A High" and "A Low" and associate them with series "A"; you will then need to select columns "B High" and "B Low" and associate them with series "B". The data in the corresponding dataset will be structured as follows:
Annotations
In the Annotations section under the Chart tab, you can create annotations by clicking the Add Annotation button. The position of each annotation is specified with the "X Location" and "Y Location" fields. If the chart's horizontal axis uses a date field, you can specify the X location in YYYY/MM/DD or YYYY format.
The following items can be added to each annotation:
- Add Text: Add text to the annotation using the Text field. Choose a Color for the text, and specify its position relative to the X and Y locations using the Text Position setting. Available positions include "Top," "Right," "Bottom," "Left," or the default "Center," which centers the text vertically and horizontally over the X and Y location.
- Add Line: Add a line annotation to your chart. Use the Direction setting to render either a "Horizontal" line, a "Vertical" line, or line in both directions ("Both"). Choose a Color for the line.
- Add Symbol: Add a symbol annotation to your chart. Select the symbol type from the Symbol dropdown, which includes options such as "Asterisk," "Circle," "Cross," "Diamond," "Hexagon," "Plus," "Square," "Star," "Times," and "Triangle." Customize the symbol’s Color and specify its Width in pixels.
