A usage about multi-dimension arrays

General Usage
1

i try to find that how to using multi-dimension arrays minus a constant in julia1.0 documents, but i fail. so can you help me? thanks

2

Do you need to subtract a scalar from each element? Then use broadcasting, eg

some_array .- some_scalar

If you need something else, please explain in detail (eg provide an example of the desired input and output).

3

xtrn[:,:,1,:] = xtrn[:,:,1,:].-rxtrn;
where xtrn is a 4 dim arrays and rxtrn is a constant.
when i run the file in this line, the peoplem as following occured.
ERROR: LoadError: syntax: extra token “rxtrn” after end of expression

4

there occur a strange thing. when i change xtrn[:,:,1,:] = xtrn[:,:,1,:].-rxtrn to xtrn[:,:,1,:] = xtrn[:,:,1,:].-rxtrn;xtr=xtrn[:,:,1,:].-rxtrn;xtrn[:,:,1,:]=xtr. it work. And the last sentence have no need to change, do you know the reason. I want to know that.

    xtrn[:,:,1,:] = xtrn[:,:,1,:].-rxtrn;
    xtr=xtrn[:,:,1,:].-rxtrn
    xtrn[:,:,1,:]=xtr;
    xtrn[:,:,2,:] = xtrn[:,:,2,:].-gxtrn;
    xtrn[:,:,3,:] = xtrn[:,:,3,:].-bxtrn;
5

Please post an MWE.

6

It may need a .= with an indexing operation ( a[] ) on the left, and with all(?) broadcast-like ( .- ) operators on the right, for the broadcast fusion optimization

a = ones(3,3,3,3);
a[:,:,1,:] .= a[:,:,1,:] .- 1;

b = ones(3,2); c = ones(2, 1);
b[:, 1] = b[:,1] * c[1,1] ##matrix multiply
7

thank you. I solved it.