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Quick Start for New Julia Users

You have some events and want an EMD number out, without learning Julia first. Copy-paste your way down this page.

1. Install Julia

On macOS or Linux:

curl -fsSL https://install.julialang.org | sh

On Windows, in PowerShell:

winget install julia -s msstore

Reopen the terminal, then confirm with julia --version.

2. Install EnergyFlow (once)

Start Julia by typing julia, then at the julia> prompt run:

using Pkg
Pkg.add("EnergyFlow")
Pkg.add("NPZ")

First time only; it takes a few minutes. (NPZ reads the .npz files below.)

3. Run it on your .npz

An event is an M × 3 array: one row per particle, columns [pT, y, φ].

Make a file my_events.jl — edit the path and the two indices to pick which events to compare:

using EnergyFlow, NPZ

data = npzread("events.npz")          # <-- your file
events = data["events"]               # <-- key holding the event array

# If events is one big padded array of shape (n, maxparticles, 3):
event_A = events[1, :, 1:3]           # <-- first event
event_B = events[2, :, 1:3]           # <-- second event

# norm=true compares shapes only; EtaPhiMetric wraps the phi coordinate.
distance = emd(event_A, event_B;
               R=1.0, beta=1.0, norm=true, metric=EtaPhiMetric())
println("EMD = ", distance)

Zero-pT padding rows are ignored automatically, so you don't need to trim them. Run it from the terminal:

julia my_events.jl        # prints e.g.  EMD = 0.633...

Two things to check if the number looks wrong: your array's column order really is [pT, y, φ] (drop or reorder columns as needed), and you picked the right dict key in data — run keys(data) to list them.

What next?