simplify the function to create particles

goal is to leave lots of room for student improvements
in class.

also, introduce missingness in the data

particlecloud/util.py

@@ -1,47 +1,46 @@
 import random
+import sys
 
-from particlecloud.stuff import Particle
+import numpy as np
 
 
-PARTICLE_FILE_COLUMN_NAMES = [
+FILE_COLUMN_NAMES = [
-    "number", "mass", "vx", "vy", "vz", "px", "py", "pz",
+    "n", "m", "v1", "v2", "v3", "p1", "p2", "p3",
 ]
 
-def make_particles(n=10):
+
-    particles = []
+def write_data_file(filename, n=20, missing_values=False):
-    for i in range(n):
+    """Write a csv file with data
-        particles.append(
+    """
-            Particle(
+
-                mass=random.gauss(mu=3., sigma=0.5),
+    with open(filename, "w") as fp:
-                velocity=(
+        fp.write(", ".join(FILE_COLUMN_NAMES) + ",\n")
-                    random.gauss(mu=0., sigma=1.5),
+        for i in range(n):
-                    random.gauss(mu=0., sigma=1.5),
+            vals = []
-                    random.gauss(mu=0., sigma=1.5),
+            vals.append(random.gauss(3., 0.5))
-                ),
+            vals.extend(
-                position=(
+                (
-                    random.gauss(mu=0., sigma=25),
+                    random.gauss(0., 25),
-                    random.gauss(mu=0., sigma=25),
+                    random.gauss(0., 25),
-                    random.gauss(mu=0., sigma=25),
+                    random.gauss(0., 25),
                 )
             )
-        )
+            vals.extend(
-    return particles
+                (
-
+                    random.gauss(0., 1.5),
-
+                    random.gauss(0., 1.5),
-def write_particles_file(filename, n=10):
+                    random.gauss(0., 1.5),
-    """Write a csv file with particle data
+                )
-    """
+            )
-    particles = make_particles(n=n)
+            if missing_values:
-    with open(filename, "w") as fp:
+                if random.randint(0,10) < 1:
-        fp.write(", ".join(PARTICLE_FILE_COLUMN_NAMES) + ",\n")
+                    idx = random.randint(1, len(vals))
-        for i, p in enumerate(particles):
+                    vals[idx] = np.nan
-            vals = []
-            vals.append(p.mass)
-            vals.extend(p.velocity)
-            vals.extend(p.position)
             line = f"{i}, " + ", ".join(f"{v:7.5f}" for v in vals) + ",\n"
             fp.write(line)
 
 
 if __name__ == '__main__':
-    write_particles_file("sample_data.csv")
+    missing_values = sys.argv[-1] == '-m'
+
+    write_data_file("sample_data.csv", n=20, missing_values=True)