Plotting shapes, chars and arrows

There are situations where you need to mark or highlight specific bars on a chart, and where a usual line plot using plot may not be optimal. Although it may be possible to do so using plot with style=plot.style_circles or style=plot.style_cross, it is often easier to use the plotshape, plotchar and plotarrow annotation functions.

plotshape

The plotshape function can display a variety of shapes. The script below will draw an “X” above all green bars:

The first parameter, data, is used as a series of logical values. The crosses are drawn on each true value. Nothing is drawn on false or na values. You may use a series of logical values or numbers as the first argument of plotshape. A 0 or na is considered a false value, any other value is considered true.

By changing the value of the style parameter, it is possible to vary the shape. The available styles are:

Shape Name	Shape	Shape with Text
shape.xcross
shape.cross
shape.circle
shape.triangleup
shape.triangledown
shape.flag
shape.arrowup
shape.arrowdown
shape.square
shape.diamond
shape.labelup
shape.labeldown

The default position where plotshape draws shapes is above bars. To use another position, use the location parameter. The following script draws a green shape.triangleup above the green bars and a red shape.triangledown below the red bars:

Possible values for the location parameter are:

• location.abovebar - above a bar.
• location.belowbar - below a bar.
• location.top - top of the script’s y space.
• location.bottom - bottom of the script’s y space.
• location.absolute - any position in the y space.

location.absolute can be used when the shapes need to be positioned more precisely in the script’s y space. The first parameter of the function is then used as a y coordinate.

‘plotshape example 2’ illustrates how the shape’s color can be defined using the color parameter and expressions which will calculate the shape’s color depending on conditions at runtime. For example:

In the given example, the first parameter of the function plotshape is true, which means that a shape is displayed at every bar. The color is calculated by the color=data ? color.green : color.red expression.

Other features of the plotshape function:

• Set the name of a displayed series of data using the title parameter.
• Shift a series of shapes to the left/right using the offset parameter.
• Set the transparency of shapes with the transp parameter.
• Use the text parameter to display a short text above/below the shape. You may use \n to separate text lines.

plotchar

The main difference between plotshape and plotchar is that with plotchar, the shape is an ASCII or Unicode symbol (provided it’s supported by the TradingView standard font) defined with the char parameter. For example:

The default character is ★ (U+2605, the “BLACK STAR” character). It’s possible to use any letter or digit and many symbols, for example: ❤, ☀, €, ⚑, ❄, ◆, ⬆, ⬇. The supported character codes are those of the Trebuchet MS font family.

The next example uses the “SNOWFLAKE” (❄, U+2744) character:

Like plotshape, the plotchar function allows you to:

• Set a shape’s color with a constant or complex arithmetic expression using the color parameter.
• Set a shape’s location with the location parameter.
• Set the name of a displayed series of data using the title parameter.
• Shift a series of shapes left/right using the offset parameter.
• Set the transparency of shapes using the transp parameter.
• Use the text parameter to display a short text above/below the shape. You may use \n to separate text lines.

plotarrow

The plotarrow annotation function allows for up/down arrows to be displayed on the chart. The arrow length is not the same on each bar and is calculated from the first parameter’s value.

The first series parameter of the plotarrow function is used to place arrows on the chart using the following logic:

• If the series value on the current bar is greater than 0, then an up arrow will be drawn, the length of which will be proportional to the relative value of the series on that bar in relation to other series values.
• If the series value on the current bar is less than 0, then a down arrow will be drawn, the length of which will be proportional to the relative value of the series on that bar in relation to other series values.
• If the series value on the current bar is equal to 0 or na then the arrow is not displayed.

Here is a simple script that illustrates how the plotarrow function works:

As you can see, the greater the relative value of the close - open difference, the longer the arrow. If close - open is greater than zero, then an up arrow is rendered. When close - open is less than zero, a down arrow is rendered.

In another example, we’ll start from the Chaikin Oscillator script in the built-in scripts and display it as an overlay above a chart using arrows:

This screenshot shows the original Chaikin Oscillator alongside the script for better understanding.

As was stated earlier, the height of the arrow is proportional to the relative value of the first series parameter. The maximum and minimum possible sizes for the arrows (in pixels) can be set using the minheight and maxheight parameters.

Additionally, the plotarrow function allows you to:

• Set the name of a displayed series of data using the title parameter.
• Set the color of an up arrow using the colorup parameter.
• Set the color of a down arrow using the colordown parameter.
• Shift a series of arrows left/right using the offset parameter.
• Set the transparency of arrows with the transp parameter.

It’s important to note that the colorup and colordown parameters must receive a constant value of the color type. Using expressions for determining color (as is done in plot, plotshape or plotchar) is not allowed.