Questions related to -0.0 and 0.0

General Usage
1

I’m using PCHIPInterpolation to do some interpolation.
itp = Interpolator(xs, ys);

This program absolutely does not allow any values in its x to be duplicates. I now have some values like the below in my data sets:
xs = [-5.0, -0.0, 0.0, 10.0, 19.0];

The interpolation would stop and give an error: “xs must be stricly increasing”. I tried to fix this issue by first using the unique function, but unique actually think they are different.

Is there a better way to address this issue?

2

See Is this a bug of the Julia function "unique"? - #30 by giordano The next patch release of 1.6, and 1.7.0 will both fix this.

TLDR is that unique currently and incorrectly uses == instead of isequal

3 Likes
3

Thanks, Oscar. I started the other thread too :slight_smile:

I’m just hoping to find an alternative solution to address the issue, so that I don’t have to wait for the next version of Julia before I can process my data.

For the NaN issue. I have decided to fill it up with some identical numerical values to get it working.

4

you could always perform minor type piracy and redefine Base.unique to do the thing it will do as of the next release. It’s not a great solution, but it will work.

5

julia> xs = [-5.0, -0.0, 0.0, 10.0, 19.0];

julia> unique(t → t == 0 ? 0.0 : t, xs)
4-element Vector{Float64}:
-5.0
-0.0
10.0
19.0

1 Like
6

Thanks. Unfortunately, I got the below error when testing:

UndefVarError: t not defined
Stacktrace:
 [1] top-level scope
   @ In[129]:3
 [2] eval
   @ ./boot.jl:360 [inlined]
 [3] include_string(mapexpr::typeof(REPL.softscope), mod::Module, code::String, filename::String)
   @ Base ./loading.jl:1116
7

No need to wait, you can just use the 1.7 release candidate

1 Like
8

I think the JuliaMono font fooled my copy and paste. That arrow really should be ->.

1 Like
9

I don’t think that will solve @leon’s problem? Since isequal(0.0, -0.0) == false the values returned by unique will still include 0.0 and -0.0…

Actually if unique is currently using == I don’t understand why both are included in the result, since

julia> 0.0 == -0.0
true
1 Like
10

It is working now! Thank you so much.

BTW, is there a way I can find the index of the elements that remained? I have another set of data y that goes with the x.

Ind = …
y = y[Ind];