Rectangle

Rectangular region of interest

Description

A Rectangle object specifies the shape and position of a rectangular region-of-interest (ROI). You can customize the appearance and interactive behavior of the ROI.

For more information about using this ROI, including keyboard shortcuts, see Tips.

Blue Rectangle ROI drawn over an object in an image.

Creation

There are two ways to create a Rectangle object. For more information, see Create ROI Shapes.

Use the drawrectangle function. Use this function when you want to create the ROI and set the appearance in a single command. You can specify the shape and position of the ROI interactively by drawing the ROI over an image using the mouse, or programmatically by using name-value arguments.
Use the images.roi.Rectangle function described here. Use this function when you want to specify the appearance and behavior of the ROI before you specify the shape and position of the ROI. After creating the object, you can specify the shape and position interactively by using the draw function or programmatically by modifying properties of the object.

Syntax

roi = images.roi.Rectangle

roi = images.roi.Rectangle(ax)

roi = images.roi.Rectangle(___,Name=Value)

Description

roi = images.roi.Rectangle creates a Rectangle object with default properties.

example

roi = images.roi.Rectangle(ax) creates an ROI in the axes specified by ax.

roi = images.roi.Rectangle(___,Name=Value) sets writeable properties using name-value arguments. You can specify multiple name-value arguments.

Example: images.roi.Rectangle(Color="y") creates a yellow colored Rectangle object.

Input Arguments

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`ax` — Parent of ROI
`gca` (default) | `Axes` object | `UIAxes` object

Parent of the ROI, specified as an Axes object or a UIAxes object. For information about using an ROI in a UI axes, including important limitations, see Using ROIs in Apps Created with App Designer.

Properties

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Shape and Position

`AspectRatio` — Aspect ratio of rectangle
`1` (default) | positive number

Aspect ratio of the rectangle, specified as a positive number. The value of this property changes automatically when you draw or resize the rectangle. The Rectangle object calculates this value as height/width.

`Position` — Position of ROI
1-by-4 numeric vector

Position of the ROI, specified as a 1-by-4 numeric vector of the form [xmin, ymin, width, height]. xmin and ymin specify the location of the upper left corner of the rectangle. width and height specify the extent of the rectangle in two dimensions.

`RotationAngle` — Angle around center of rectangle
`0` (default) | numeric scalar

Angle around the center of the rectangle, specified as a numeric scalar. The angle is measured in degrees in a clockwise direction. The value of this property changes automatically when you draw or move the ROI.

The value of RotationAngle does not impact the values in the Position property. The Position property represents the initial position of the ROI, before rotation. To determine the location of a rotated ROI, use the Vertices property.

`Vertices` — Locations of points on edge of rectangle
Read-only: 4-by-2 numeric matrix

This property is read-only.

Locations of points on the corners of the ROI, returned as a 4-by-2 numeric matrix.

Color and Styling

`Color` — ROI color
`[0 0.4470 0.7410]` (default) | RGB triplet | color name | short color name

ROI color, specified as an RGB triplet, a color name, or a short color name.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0, 1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB^® uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: Color="r"

Example: Color="green"

Example: Color=[0 0.4470 0.7410]

`FaceAlpha` — Transparency of ROI face
`0.2` (default) | number in the range [0, 1]

Transparency of the ROI face, specified as a number in the range [0, 1]. When the value is 1, the ROI face is completely opaque. When the value is 0, the ROI face is completely transparent.

`LineWidth` — Width of ROI border
positive number

Width of the ROI border, specified as a positive number in points. The default value is three times the number of points per screen pixel, such that the border is three pixels wide.

`MarkerSize` — Marker size
positive number

Marker size, specified as a positive number in points. The default value is eight times the number of points per screen pixel, such that markers are eight pixels in size.

`SelectedColor` — Color of ROI when selected
`"none"` (default) | RGB triplet | color name | short color name

Color of the ROI when selected, specified as an RGB triplet, a color name, a short color name, or "none". If you specify "none", then the value of Color defines the color of the ROI for all states, selected or not.

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: SelectedColor="r"

Example: SelectedColor="green"

Example: SelectedColor=[0 0.4470 0.7410]

`StripeColor` — Color of ROI stripe
`"none"` (default) | RGB triplet | color name | short color name

Color of the ROI stripe, specified as an RGB triplet, a color name, a short color name, or "none". If you specify "none", then the ROI edge is a solid color specified by Color. Otherwise, the edge of the ROI is striped, with colors alternating between the colors specified by Color and StripeColor.

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: StripeColor="r"

Example: StripeColor="green"

Example: StripeColor=[0 0.4470 0.7410]

`Visible` — ROI visibility
`"on"` (default) | `"off"` | on/off logical value

ROI visibility, specified as "on" or "off", or as a numeric or logical 0 (false) or 1 (true). A value of "on" is equivalent to true, and "off" is equivalent to false. The value is stored as an on/off logical value of type OnOffSwitchState.

Value	Description
`"on"`	Display the ROI.
`"off"`	Hide the ROI without deleting it. You still can access the properties of an invisible ROI.

Labels

`Label` — ROI label
`''` (default) | character vector | string scalar

ROI label, specified as a character vector or string scalar. By default, the ROI has no label ('').

`LabelAlpha` — Transparency of text background
`1` (default) | number in the range [0, 1]

Transparency of the text background, specified as a number in the range [0, 1]. When set to 1, the text background is completely opaque. When set to 0, the text background is completely transparent.

`LabelTextColor` — Label text color
`"black"` (default) | RGB triplet | color name | short color name

Label text color, specified as an RGB triplet, a color name, or a short color name.

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet
`"red"`	`"r"`	`[1 0 0]`
`"green"`	`"g"`	`[0 1 0]`
`"blue"`	`"b"`	`[0 0 1]`
`"cyan"`	`"c"`	`[0 1 1]`
`"magenta"`	`"m"`	`[1 0 1]`
`"yellow"`	`"y"`	`[1 1 0]`
`"black"`	`"k"`	`[0 0 0]`
`"white"`	`"w"`	`[1 1 1]`

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
`[0 0.4470 0.7410]`
`[0.8500 0.3250 0.0980]`
`[0.9290 0.6940 0.1250]`
`[0.4940 0.1840 0.5560]`
`[0.4660 0.6740 0.1880]`
`[0.3010 0.7450 0.9330]`
`[0.6350 0.0780 0.1840]`

Example: LabelTextColor="r"

Example: LabelTextColor="green"

Example: LabelTextColor=[0 0.4470 0.7410]

`LabelVisible` — Visibility of ROI label
`"on"` (default) | `"off"` | `"hover"` | `"inside"`

Visibility of the ROI label, specified as one of these values:

Value	Description
`"on"`	Label is visible when the ROI is visible and the `Label` property is nonempty (default).
`"hover"`	Label is visible only when the mouse hovers over the ROI.
`"inside"`	Label is visible only when there is adequate space inside the ROI to display it.
`"off"`	Label is not visible.

Interactivity

`ContextMenu` — Context menu
`ContextMenu` object

Context menu that displays when you right-click the ROI, specified as a ContextMenu object. You can create a custom context menu by using the uicontextmenu function and then configuring context menu properties.

`Deletable` — Context menu provides option to delete the ROI
`true` or `1` (default) | `false` or `0`

Context menu provides an option to delete the ROI, specified as a numeric or logical 1 (true) or 0 (false). When the value is true, you can delete the ROI interactively using the context menu. When the value is false, the context menu option to delete the ROI is disabled.

In both cases, you can delete the ROI outside of the context menu by using the delete function.

`DrawingArea` — Area of axes in which you can interactively place ROI
`"auto"` (default) | `"unlimited"` | `[x,y,w,h]`

Area of the axes in which you can interactively place the ROI, specified as one of the values in this table.

Value	Description
`"auto"`	The drawing area is the current axes limits (default).
`"unlimited"`	The drawing area has no boundary and ROIs can be drawn or dragged to extend beyond the axes limits.
`[x,y,w,h]`	The drawing area is restricted to a rectangular region beginning at (x,y), and extending to width w and height h.

`FaceSelectable` — ROI face can capture clicks
`true` or `1` (default) | `false` or `0`

ROI face can capture clicks, specified as a numeric or logical 1 (true) or 0 (false). When true, the ROI face captures mouse clicks. When false, the ROI face does not capture mouse clicks.

`FixedAspectRatio` — Aspect ratio remains constant
`false` or `0` (default) | `true` or `1`

Aspect ratio remains constant during interaction, specified as a numeric or logical 0 (false) or 1 (true). When the value is true, the aspect ratio remains constant when you draw or resize the ROI. When the value is false, you can change the aspect ratio when drawing or resizing the ROI. You can change the state of this property using the default context menu.

`InteractionsAllowed` — Interactivity of ROI
`"all"` (default) | `"none"` | `"translate"`

Interactivity of the ROI, specified as one of the values in this table.

Value	Description
`"all"`	You can fully interact with the ROI. Reshape the ROI by changing the position of individual vertices, or translate (move) the entire ROI.
`"none"`	You cannot interact with the ROI or access the context menu. No drag points are visible.
`"translate"`	You can translate the entire ROI within the drawing area. The relative position of vertices is fixed and you cannot reshape the ROI.

You can access the context menu for all values of InteractionsAllowed except "none".

`Rotatable` — Rectangle can be rotated
`false` or `0` (default) | `true` or `1`

Rectangle can be rotated, specified as a numeric or logical 0 (false) or 1 (true). When the value is false (default), the rectangle cannot be rotated. When the value is true, you can rotate the rectangle by clicking near the markers at the corners.

`Selected` — Selection state of ROI
`false`, `0`, or `"off"` (default) | `true`, `1`, or `"on"`

Selection state of the ROI, specified as "off" or "on", or as a numeric or logical 0 (false) or 1 (true). A value of "off" is equivalent to false, and "on" is equivalent to true.

You can also set this property interactively. For example, clicking on the ROI selects the ROI and sets this property to true. Similarly, pressing the Ctrl key and clicking the ROI deselects the ROI and sets the value of this property to false.

Parent/Child

`HandleVisibility` — Visibility of ROI handle in `Children` property of parent
`"on"` (default) | `"off"` | `"callback"`

Visibility of the ROI handle in the Children property of the parent, specified as one of the values in this table.

Value	Description
`"on"`	The object handle is always visible (default).
`"off"`	The object handle is hidden at all times.
`"callback"`	The object handle is visible from within callbacks or functions invoked by callbacks, but not from within functions invoked from the command line.

`Parent` — ROI parent
`Axes` object | `UIAxes` object

ROI parent, specified as an Axes or UIAxes object. For information about using an ROI in a UI axes, including important limitations, see Using ROIs in Apps Created with App Designer.

Identifiers

`Tag` — Tag to associate with ROI
`''` (default) | character vector | string scalar

Tag to associate with the ROI, specified as a character vector or string scalar. Use the tag value to find the ROI object in a hierarchy of objects using the findobj function.

`UserData` — Data to associate with ROI
any MATLAB data

Data to associate with the ROI, specified as any MATLAB data. For example, you can specify a scalar, vector, matrix, cell array, string, character array, table, or structure. The Rectangle object does not use this data.

Object Functions

`addlistener`	Create event listener bound to event source
`beginDrawingFromPoint`	Begin drawing ROI from specified point
`bringToFront`	Bring ROI to front of Axes stacking order
`createMask`	Create binary mask image from ROI
`draw`	Begin drawing ROI interactively
`inROI`	Query if points are located in ROI
`wait`	Block MATLAB command line until ROI operation is finished

Examples

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Create Rectangular ROI Non-interactively

Open Live Script

Read image into the workspace and display it.

I = imread('baby.jpg');
figure
imshow(I)

Figure contains an axes object. The hidden axes object contains an object of type image.

Create a rectangular ROI on the image, using the Position parameter to specify its location and size. The example also specifies that the edge of the rectangle is a striped line. For programmatically created ROIs, if you want the ROI drawn in a specific axes, you must specify that axes as an input argument. Otherwise, an instance of the images.roi.Rectangle class is created but not displayed. In this example, specify the current axes (gca) to draw the ROI on the image in that axes.

h = images.roi.Rectangle(gca,'Position',[500,500,1000,1000],'StripeColor','r');

Figure contains an axes object. The hidden axes object contains 2 objects of type image, images.roi.rectangle.

Set Up Listeners for Rectangle ROI Events

Open Live Script

Read and display image.

I = imread("cameraman.tif");
imshow(I)

Create a Rectangle ROI in the same axes as the image, then add listeners for ROI moving events.

roi = images.roi.Rectangle(gca);
addlistener(roi,"MovingROI",@allevents);
addlistener(roi,"ROIMoved",@allevents);

Draw the Rectangle ROI interactively. Then, invoke the allevents callback function by moving the ROI. When you move the ROI, the listeners send notifications of these events and execute the callback function.

draw(roi)

Figure contains an axes object. The axes object contains 2 objects of type image, images.roi.rectangle.

The allevents callback function displays at the command line the previous position and the current position of the ROI.

function allevents(src,evt)
evname = evt.EventName;
    switch evname
        case "MovingROI"
            disp("ROI moving. Previous position: "+mat2str(evt.PreviousPosition));
            disp("ROI moving. Current position:  "+mat2str(evt.CurrentPosition));
        case "ROIMoved"
            disp("ROI moved. Previous position: "+mat2str(evt.PreviousPosition));
            disp("ROI moved. Current position:  "+mat2str(evt.CurrentPosition));
    end
end

More About

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Events

To receive notification from the ROI when certain events happen, set up listeners for these events. You can specify a callback function that executes when one of these events occurs. When the ROI notifies your application through the listener, it returns data specific to the event. Look at the event class for the specific event to see what is returned.

For an example, see Set Up Listeners for Rectangle ROI Events.

Event Name	Trigger	Event Data	Event Attributes
`DeletingROI`	ROI is about to be interactively deleted.	`event.EventData`	`NotifyAccess`: `private` `ListenAccess`: `public`
`DrawingStarted`	ROI is about to be interactively drawn.	`event.EventData`	`NotifyAccess`: `private` `ListenAccess`: `public`
`DrawingFinished`	ROI has been interactively drawn.	`event.EventData`	`NotifyAccess`: `private` `ListenAccess`: `public`
`MovingROI`	ROI shape or location is being interactively changed.	`images.roi.RectangleMovingEventData`	`NotifyAccess`: `private` `ListenAccess`: `public`
`ROIMoved`	ROI shape or location has been interactively changed.	`images.roi.RectangleMovingEventData`	`NotifyAccess`: `private` `ListenAccess`: `public`
`ROIClicked`	ROI has been clicked.	`images.roi.ROIClickedEventData`	`NotifyAccess`: `private` `ListenAccess`: `public`

Tips

To draw the ROI interactively using the draw or drawrectangle function, position the cursor on the axes and click and drag to create the shape. To finish the ROI, release the mouse button.

The ROI supports the following interactivity, including keyboard shortcuts.

Behavior	Keyboard shortcut
Cancel drawing the ROI.	Press Esc. The function returns a valid ROI object with an empty `Position` property.
Resize (reshape) the ROI.	Position the cursor over a vertex and then click and drag. The rectangle has vertices at each corner and at the midpoint of each side. To preserve the aspect ratio while resizing, press the Shift key. To lock the aspect ratio, use the Fix Aspect Ratio in the right-click context menu.
Move the ROI.	Position the cursor over the ROI. The cursor changes to the fleur shape. Click and drag the ROI.
Delete the ROI.	Position the pointer on the rectangle, right-click, and choose Delete Rectangle from the context menu. You can also delete the ROI programmatically using the `delete` function.

For information about using an ROI in an app created with App Designer, see Using ROIs in Apps Created with App Designer.

Version History

Introduced in R2018b

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R2020a: `UIContextMenu` property is not recommended

Starting in R2020a, using the UIContextMenu property to assign a context menu to a graphics object or UI component is not recommended. Use the ContextMenu property instead. The property values are the same.

There are no plans to remove support for the UIContextMenu property at this time. However, the UIContextMenu property no longer appears in the list returned by calling the get function on a graphics object or UI component.

Rectangle

Description

Creation

Syntax

Description

Input Arguments

ax — Parent of ROI gca (default) | Axes object | UIAxes object

Properties

Shape and Position

AspectRatio — Aspect ratio of rectangle 1 (default) | positive number

Position — Position of ROI 1-by-4 numeric vector

RotationAngle — Angle around center of rectangle 0 (default) | numeric scalar

Vertices — Locations of points on edge of rectangle Read-only: 4-by-2 numeric matrix

Color and Styling

Color — ROI color [0 0.4470 0.7410] (default) | RGB triplet | color name | short color name

FaceAlpha — Transparency of ROI face 0.2 (default) | number in the range [0, 1]

LineWidth — Width of ROI border positive number

MarkerSize — Marker size positive number

SelectedColor — Color of ROI when selected "none" (default) | RGB triplet | color name | short color name

StripeColor — Color of ROI stripe "none" (default) | RGB triplet | color name | short color name

Visible — ROI visibility "on" (default) | "off" | on/off logical value

Labels

Label — ROI label '' (default) | character vector | string scalar

LabelAlpha — Transparency of text background 1 (default) | number in the range [0, 1]

LabelTextColor — Label text color "black" (default) | RGB triplet | color name | short color name

LabelVisible — Visibility of ROI label "on" (default) | "off" | "hover" | "inside"

Interactivity

ContextMenu — Context menu ContextMenu object

Deletable — Context menu provides option to delete the ROI true or 1 (default) | false or 0

DrawingArea — Area of axes in which you can interactively place ROI "auto" (default) | "unlimited" | [x,y,w,h]

FaceSelectable — ROI face can capture clicks true or 1 (default) | false or 0

FixedAspectRatio — Aspect ratio remains constant false or 0 (default) | true or 1

InteractionsAllowed — Interactivity of ROI "all" (default) | "none" | "translate"

Rotatable — Rectangle can be rotated false or 0 (default) | true or 1

Selected — Selection state of ROI false, 0, or "off" (default) | true, 1, or "on"

Parent/Child

HandleVisibility — Visibility of ROI handle in Children property of parent "on" (default) | "off" | "callback"

Parent — ROI parent Axes object | UIAxes object

Identifiers

Tag — Tag to associate with ROI '' (default) | character vector | string scalar

UserData — Data to associate with ROI any MATLAB data

Object Functions

Examples

Create Rectangular ROI Non-interactively

Set Up Listeners for Rectangle ROI Events

More About

Events

Tips

Version History

R2020a: UIContextMenu property is not recommended

See Also

Topics

`ax` — Parent of ROI
`gca` (default) | `Axes` object | `UIAxes` object

`AspectRatio` — Aspect ratio of rectangle
`1` (default) | positive number

`Position` — Position of ROI
1-by-4 numeric vector

`RotationAngle` — Angle around center of rectangle
`0` (default) | numeric scalar

`Vertices` — Locations of points on edge of rectangle
Read-only: 4-by-2 numeric matrix

`Color` — ROI color
`[0 0.4470 0.7410]` (default) | RGB triplet | color name | short color name

`FaceAlpha` — Transparency of ROI face
`0.2` (default) | number in the range [0, 1]

`LineWidth` — Width of ROI border
positive number

`MarkerSize` — Marker size
positive number

`SelectedColor` — Color of ROI when selected
`"none"` (default) | RGB triplet | color name | short color name

`StripeColor` — Color of ROI stripe
`"none"` (default) | RGB triplet | color name | short color name

`Visible` — ROI visibility
`"on"` (default) | `"off"` | on/off logical value

`Label` — ROI label
`''` (default) | character vector | string scalar

`LabelAlpha` — Transparency of text background
`1` (default) | number in the range [0, 1]

`LabelTextColor` — Label text color
`"black"` (default) | RGB triplet | color name | short color name

`LabelVisible` — Visibility of ROI label
`"on"` (default) | `"off"` | `"hover"` | `"inside"`

`ContextMenu` — Context menu
`ContextMenu` object

`Deletable` — Context menu provides option to delete the ROI
`true` or `1` (default) | `false` or `0`

`DrawingArea` — Area of axes in which you can interactively place ROI
`"auto"` (default) | `"unlimited"` | `[x,y,w,h]`

`FaceSelectable` — ROI face can capture clicks
`true` or `1` (default) | `false` or `0`

`FixedAspectRatio` — Aspect ratio remains constant
`false` or `0` (default) | `true` or `1`

`InteractionsAllowed` — Interactivity of ROI
`"all"` (default) | `"none"` | `"translate"`

`Rotatable` — Rectangle can be rotated
`false` or `0` (default) | `true` or `1`

`Selected` — Selection state of ROI
`false`, `0`, or `"off"` (default) | `true`, `1`, or `"on"`

`HandleVisibility` — Visibility of ROI handle in `Children` property of parent
`"on"` (default) | `"off"` | `"callback"`

`Parent` — ROI parent
`Axes` object | `UIAxes` object

`Tag` — Tag to associate with ROI
`''` (default) | character vector | string scalar

`UserData` — Data to associate with ROI
any MATLAB data

R2020a: `UIContextMenu` property is not recommended