Undefined variable "vision" or class "vision.OpticalFlow" in Matlab 2018a

Question

I have Matlab 2018a (linux version) installed on my Ubuntu machine. I am trying to calculate the optical flow of a video where I am presented with the above error. A Google search suggests that this can be cause by two problems, either having an old version of Matlab (like 2009) or the Computer vision toolbox may not be installed.

I have the latest version of Matlab and still am getting this error and I also have the required toolbox installed as can be seen from the output command of ver

>> ver
-----------------------------------------------------------------------------------------------------
MATLAB Version: 9.4.0.813654 (R2018a)
MATLAB License Number: 893265
Operating System: Linux 4.13.0-38-generic #43~16.04.1-Ubuntu SMP Wed Mar 14 17:48:43 UTC 2018 x86_64
Java Version: Java 1.8.0_144-b01 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
-----------------------------------------------------------------------------------------------------
MATLAB                                                Version 9.4         (R2018a)
Simulink                                              Version 9.1         (R2018a)
Aerospace Blockset                                    Version 3.21        (R2018a)
Aerospace Toolbox                                     Version 2.21        (R2018a)
Antenna Toolbox                                       Version 3.1         (R2018a)
Audio System Toolbox                                  Version 1.4         (R2018a)
Automated Driving System Toolbox                      Version 1.2         (R2018a)
Bioinformatics Toolbox                                Version 4.10        (R2018a)
Communications System Toolbox                         Version 6.6         (R2018a)
Computer Vision System Toolbox                        Version 8.1         (R2018a)
Control System Toolbox                                Version 10.4        (R2018a)
Curve Fitting Toolbox                                 Version 3.5.7       (R2018a)
DSP System Toolbox                                    Version 9.6         (R2018a)
Database Toolbox                                      Version 8.1         (R2018a)
Datafeed Toolbox                                      Version 5.7         (R2018a)
Econometrics Toolbox                                  Version 5.0         (R2018a)
Embedded Coder                                        Version 7.0         (R2018a)
Filter Design HDL Coder                               Version 3.1.3       (R2018a)
Financial Instruments Toolbox                         Version 2.7         (R2018a)
Financial Toolbox                                     Version 5.11        (R2018a)
Fixed-Point Designer                                  Version 6.1         (R2018a)
Fuzzy Logic Toolbox                                   Version 2.3.1       (R2018a)
GPU Coder                                             Version 1.1         (R2018a)
Global Optimization Toolbox                           Version 3.4.4       (R2018a)
HDL Coder                                             Version 3.12        (R2018a)
HDL Verifier                                          Version 5.4         (R2018a)
Image Acquisition Toolbox                             Version 5.4         (R2018a)
Image Processing Toolbox                              Version 10.2        (R2018a)
Instrument Control Toolbox                            Version 3.13        (R2018a)
LTE HDL Toolbox                                       Version 1.1         (R2018a)
LTE System Toolbox                                    Version 2.6         (R2018a)
MATLAB Coder                                          Version 4.0         (R2018a)
MATLAB Compiler                                       Version 6.6         (R2018a)
MATLAB Compiler SDK                                   Version 6.5         (R2018a)
MATLAB Report Generator                               Version 5.4         (R2018a)
Mapping Toolbox                                       Version 4.6         (R2018a)
Model Predictive Control Toolbox                      Version 6.1         (R2018a)
Neural Network Toolbox                                Version 11.1        (R2018a)
Optimization Toolbox                                  Version 8.1         (R2018a)
Parallel Computing Toolbox                            Version 6.12        (R2018a)
Partial Differential Equation Toolbox                 Version 3.0         (R2018a)
Phased Array System Toolbox                           Version 3.6         (R2018a)
Polyspace Bug Finder                                  Version 2.5         (R2018a)
Polyspace Code Prover                                 Version 9.9         (R2018a)
Powertrain Blockset                                   Version 1.3         (R2018a)
Predictive Maintenance Toolbox                        Version 1.0         (R2018a)
RF Blockset                                           Version 7.0         (R2018a)
RF Toolbox                                            Version 3.4         (R2018a)
Risk Management Toolbox                               Version 1.3         (R2018a)
Robotics System Toolbox                               Version 2.0         (R2018a)
Robust Control Toolbox                                Version 6.4.1       (R2018a)
Signal Processing Toolbox                             Version 8.0         (R2018a)
SimBiology                                            Version 5.8         (R2018a)
SimEvents                                             Version 5.4         (R2018a)
Simscape                                              Version 4.4         (R2018a)
Simscape Driveline                                    Version 2.14        (R2018a)
Simscape Electronics                                  Version 2.13        (R2018a)
Simscape Fluids                                       Version 2.4         (R2018a)
Simscape Multibody                                    Version 5.2         (R2018a)
Simscape Power Systems                                Version 6.9         (R2018a)
Simulink 3D Animation                                 Version 8.0         (R2018a)
Simulink Check                                        Version 4.1         (R2018a)
Simulink Code Inspector                               Version 3.2         (R2018a)
Simulink Coder                                        Version 8.14        (R2018a)
Simulink Control Design                               Version 5.1         (R2018a)
Simulink Coverage                                     Version 4.1         (R2018a)
Simulink Design Optimization                          Version 3.4         (R2018a)
Simulink Design Verifier                              Version 3.5         (R2018a)
Simulink Report Generator                             Version 5.4         (R2018a)
Simulink Requirements                                 Version 1.1         (R2018a)
Simulink Test                                         Version 2.4         (R2018a)
Stateflow                                             Version 9.1         (R2018a)
Statistics and Machine Learning Toolbox               Version 11.3        (R2018a)
Symbolic Math Toolbox                                 Version 8.1         (R2018a)
System Identification Toolbox                         Version 9.8         (R2018a)
Text Analytics Toolbox                                Version 1.1         (R2018a)
Trading Toolbox                                       Version 3.4         (R2018a)
Vehicle Dynamics Blockset                             Version 1.0         (R2018a)
Vehicle Network Toolbox                               Version 4.0         (R2018a)
Vision HDL Toolbox                                    Version 1.6         (R2018a)
WLAN System Toolbox                                   Version 1.5         (R2018a)
Wavelet Toolbox                                       Version 5.0         (R2018a)

When calculating the OpticalFlow using the command opticalFlowClass = vision.OpticalFlow('OutputValue', Horizontal and vertical components in complex form', 'Method', 'Horn-Schunck') I get the following error:

Undefined variable "vision" or class "vision.OpticalFlow".

Error in Video2OpticalFlow (line 28)
        opticalFlowClass = vision.OpticalFlow('OutputValue', ...

Can someone please guide me as to why I am getting this error? Thank you

Answer 1

I found out why its not working.. vision.OpticalFlow has been removed from the latest version of Matlab, we are advised to use opticalFlowHS instead if using the Horn-Schunck method

more details here: https://uk.mathworks.com/help/vision/ref/opticalflow-class.html