jointPositionFromJointName

R2026b

Get joint position index in configuration vector from joint name

Since R2026b

Syntax

startIdx = jointPositionFromJointName(robot,jointname)

[startIdx,endIdx] = jointPositionFromJointName(robot,jointname)

Description

startIdx = jointPositionFromJointName(robot,jointname) returns the index of the configuration‑vector element of the specified joint in the rigid body tree robot model.

[startIdx,endIdx] = jointPositionFromJointName(robot,jointname) returns the start and end indices of the configuration‑vector elements of the specified joint in the rigid body tree robot model.

Examples

Set Configuration Vector Element by Joint Name

Load the Rethink Sawyer robot and show the configuration vector for the home configuration. Sawyer contains 20 joints, many of them being fixed joints that do not contribute elements to the configuration vector.

robot = loadrobot("rethinkSawyer",DataFormat="row");
config = robot.homeConfiguration

config = 1×8
0	0	0	0	0	0	0	0

Get the configuration-vector index of the "head_pan" joint and set the corresponding configuration vector element to pi radians.

headIdx = jointPositionFromJointName(robot,"head_pan");
config(headIdx) = pi;

Input Arguments

robot — Rigid body tree robot model

rigidBodyTree object

Rigid body tree robot model, specified as a rigidBodyTree object.

jointname — Joint name

string scalar | character vector

Joint name, specified as a string scalar or character vector.

Output Arguments

startIdx — Start index of joint in configuration vector

nonnegative integer | 0

Start index of the joint in the configuration vector, returned as a nonnegative integer. startIdx is a positive integer for joints that contribute position degrees of freedom. If the joint is fixed, startIdx is 0, indicating that the joint has no corresponding element in the configuration vector.

endIdx — End index of the joint in the configuration vector

integer | -1

End index of the joint in the configuration vector, returned as an integer. endIdx is an integer for joints that contribute position degrees of freedom. If the joint is fixed, endIdx is -1, indicating that the joint has no corresponding element in the configuration vector.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2026b