The MATLAB R2018b release notes report a number of performance improvements, including faster startup and faster calls to built-in functions. I pick out here a few other highlights from the release (excluding the toolboxes) that are of interest from the numerical analysis point of view.

The new `xline`

and `yline`

functions add vertical or horizontal lines to a plot—something that I have needed from time to time and have previously had to produce with a `line`

or a `plot`

command, together with `hold on`

. For example, `xline(pi)`

plots a vertical line at `x = pi`

.

The `stackedplot`

function is mainly of interest for plotting multiple variables from a table in a single plot, but it can also plot the columns of a matrix. In this example, `A`

is the symmetric eigenvector matrix for the second difference matrix:

A = gallery('orthog',10,1); stackedplot(A);

The resulting plot clearly shows that the number of sign changes increases with the column index.

String arrays, introduced in R2016b, are now supported throughout MATLAB. In the previous example I could have typed `A = gallery("orthog",10,1)`

.

A new option `'all'`

to the functions `all`

, `any`

, `max`

, `min`

, `prod`

, `sum`

(and a few others) makes them operate on all the dimensions of the array. For example:

>> A = pascal(3) A = 1 1 1 1 2 3 1 3 6 >> max(A,[],'all') ans = 6 >> [prod(A,'all'), sum(A,'all')] ans = 108 19

The empty second argument in the `max`

call is needed because `max(x,y)`

is also a supported usage. This is a useful addition. I have often written `norm(A(:),inf)`

to avoid `max(max(abs(A)))`

(which does not work for arrays with more than two dimensions), but now I can write `max(abs(A),[],'all')`

without incurring the overhead of forming `A(:)`

.

New functions `sinpi`

and `cospi`

plot the sine and cosine functions at the specified multiple of . Thus `sinpi(x)`

is the same as `sin(pi*x)`

except that it does not explicitly compute `pi*x`

and so returns exact answers for integer arguments:

>> [sin(pi) sinpi(1)] ans = 1.2246e-16 0

- For earlier “What’s New in MATLAB” posts click here.
- See also MATLAB Guide, Third Edition (2017).