Summary of important uservisible changes for version 5
February 23, 2019
General improvements

The Octave plotting system now supports high resolution screens, i.e., those with greater than 96 DPI which are referred to as HiDPI/Retina monitors.

Unicode character support for files and folders in Windows.

A new core function
movfun
will apply a function to a sliding window of arbitrary size on a dataset and accumulate the results. Many common cases have been implemented using the naming schememovXXX
whereXXX
is the function that will be applied. For example, the moving average over a dataset ismovmean
. New moving window functions:movfun
movslice
movmad
movmax
movmean
movmedian
movmin
movprod
movstd
movsum
movvar

The
fsolve
function has been tweaked to use larger step sizes when calculating the Jacobian of a function with finite differences. This leads to faster convergence. 
The
ranks
function has been recoded for performance and is now 25X faster. In addition, it now supports a third argument that specifies how to resolve the ranking of tie values. 
The function
randi
has been recoded to produce an unbiased (all results are equally likely) sample of integers. This may produce different results in existing code. If it is necessary to reproduce the exact random integer sequence as in previous versions useri = imin + floor ((imax  imin + 1) * rand ());

The function
isdefinite
now returnstrue
orfalse
rather than1
,0
, or1
. To test for a positive semidefinite matrix (old output of0
) check whether the following two conditions hold:isdefinite (A) => 0
andisdefinite (A + 5*TOL, TOL) => 1

The
intmax
,intmin
, andflintmax
functions now accept a variable as input. Existing code to query the range of an existing variable can be simplified by removing the call toclass
that was previously required. For example defining the variablex = int8 (3)
in the workspace, calls likerange = [ intmin(class(x)), intmax(class(x)) ]
can in Octave 5 be simplified to
range = [ intmin(x), intmax(x) ]
. 
The path handling functions no longer perform variable or brace expansion on path elements and Octave’s loadpath is no longer subject to these expansions.

A new printing device is available,
"ddumb"
, which produces ASCII art for plots. This device is only available with the gnuplot toolkit.
Dependencies

The GUI requires Qt libraries. The minimum Qt4 version supported is Qt4.8. Qt5 of any version is preferred.

The OSMesa library is no longer used. To print invisible figures when using OpenGL graphics, the Qt
QOFFSCREENSURFACE
feature must be available and you must use the qt graphics toolkit. 
The FFTW library is now required to perform FFT calculations. The FFTPACK sources have been removed from Octave.
Matlab compatibility

The determination of an object’s dimensions, size, and shape by the functions
ndims
,rows
,columns
,isscalar
,isvector
,isrow
,iscolumn
,ismatrix
, andissquare
now fully depends on the function size. Thus, any userdefined object can ensure correct treatment by the aforementioned functions by properly overloading thesize
function. 
The functions
issymmetric
andishermitian
accept an option"nonskew"
or"skew"
to calculate the symmetric or skewsymmetric property of a matrix. Performance has also been increased. 
The
issorted
function now uses a direction option of"ascend"
or"descend"
. Change all uses of"ascending"
and"descending"
in existing code to the new options. 
The
strncmp
andstrncmpi
functions now returntrue
if the two input strings match, even though the number of characters specified byn
exceeds the string length. For Example:strncmp ("abc", "abc", 100)
returns
true
in Octave 5 andfalse
in older versions of Octave. 
The
str2func
function no longer accepts a second"global"
argument. This argument was typically used to allow functions that accept function names as arguments to avoid conflicts with subfunctions or nested functions. Instead, it’s best to avoid this situation entirely and require users to pass function handles rather than function names. 
Using
clear
with no arguments now removes only local variables from the current workspace. Global variables will no longer be visible, but they continue to exist in the global workspace and possibly other workspaces such as the base workspace.
Nonlinear Equations
Several default solver options have been changed to be Matlab compatible. This may result in existing code producing different results.

fsolve
Option New Default Old Default FinDiffType
"forward"
"central"
MaxFunEvals
100*length(x0)
Inf
TolFun
1e6
1e7
TolX
1e6
1e7
Updating
"off"
"on"

fminsearch
Option New Default Old Default TolFun
1e7
1e4

fminbnd
Option New Default Old Default MaxFunEvals
500
Inf
MaxIter
500
Inf
TolX
1e4
1e8

fminunc
Option New Default Old Default FinDiffType
"forward"
"central"
MaxFunEvals
100*length(x0)
Inf
TolX
1e6
1e7
TolFun
1e6
1e7
Graphic objects

Figure graphic objects have a new property
"Number"
which is readonly and will return the handle (number) of the figure. However, if the property"IntegerHandle"
has been set to"off"
then the property will return an empty matrix[]
. 
Patch and surface graphic objects now use the
"FaceNormals"
property for flat lighting. 
"FaceNormals"
and"VertexNormals"
for patch and surface graphic objects are now calculated only when necessary to improve graphics performance. In order for any normals to be calculated the"FaceLighting"
property must be set to"flat"
(FaceNormals) or"gouraud"
(VertexNormals), and a light object must be present in the axes. 
The
"Margin"
property oftext
objects has a new default of3
rather than2
. 
Printing to raster formats (bitmaps like PNG or JPEG) now uses an OpenGLbased method by default. The print options
"opengl"
(raster) and"painters"
(vector) have been added (“qt” toolkit only). The figure property"renderer"
specifies which renderer to use. When the property"renderermode"
is"auto"
Octave will select"opengl"
for a raster output format and"painters"
for a vector output format. 
A new print option
"RGBImage"
has been added which captures the pixels of a figure as an image. This is similar to screen capture tools, except that print formatting options can be used to, for example, change the resolution or display the image in black and white. 
Two new print options for pagebased formats (PDF, PostScript) have been added. The
"fillpage"
option will stretch the plot to occupy the entire page with 0.25 inch margins all around. The"bestfit"
option will expand the plot to take up as much room as possible on the page without distorting the original aspect ratio of the plot. 
Printing using the
"dtiff"
output device will now create compressed images using LZW compression. To produce uncompressed images use the"dtiffn"
device.
Legacy functions
The following functions have been declared legacy functions which means they are obsolete and should not be used in any new code. Unlike deprecated functions, however, their removal from Octave has not yet been scheduled.
Function  Replacement 

findstr 
strfind 
flipdim 
flip 
isdir 
isfolder or dir_in_loadpath 
isequalwithequalnans 
isequaln 
isstr 
ischar 
setstr 
char 
strmatch 
strncmp or strcmp 
strread 
textscan 
textread 
textscan 
Deprecated functions and properties
The following functions and graphics properties have been deprecated in Octave 5 and will be removed from Octave 7 (or whatever version is the second major release after 5):

Functions
Function Replacement output_max_field_width
output_precision
is_keyword
iskeyword

Graphics properties
Object Property Value text
fontangle
"oblique"
uibuttongroup
fontangle
"oblique"
uicontrol
fontangle
"oblique"
uipanel
fontangle
"oblique"
uitable
fontangle
"oblique"

Specifying
legend
position with a numeric argument is deprecated. Use a string argument instead. 
The environment variable used by
mkoctfile
for linker flags is nowLDFLAGS
rather thanLFLAGS
.LFLAGS
is deprecated, and a warning is emitted if is used, but it will continue to work.
Removed functions and properties
The following functions and properties were deprecated in Octave 4.2 and have been removed from Octave 5.

Functions
Function Replacement bitmax
flintmax
mahalanobis
mahal
in Octave Forge statistics pkgmd5sum
hash
octave_config_info
__octave_config_info__
onenormest
normest1
sleep
pause
usleep
pause
wavread
audioread
wavwrite
audiowrite

Properties
Object Property Value axes
xaxislocation
"zero"
yaxislocation
"zero"
hggroup
erasemode
image
erasemode
line
erasemode
patch
erasemode
patch
normalmode
surface
erasemode
surface
normalmode
text
erasemode
Alphabetical list of new functions added in 5
clearvars
isfile
isfolder
matlab.lang.makeUniqueStrings
matlab.lang.makeValidName
movegui
movfun
movie
movmad
movmax
movmean
movmedian
movmin
movprod
movslice
movstd
movsum
movvar
openfig
ordeig
savefig
uitable