Using apply function Dataframe - python-3.x

Question

I need help correcting an error I am getting.
I have the following dataframe:
x = [-0.75853, -0.75853, -0.75853, -0.75852]
y = [-0.63435, -0.63434, -0.63435, -0.63436]
z = [-0.10488, -0.10490, -0.10492, -0.10495]
w = [-0.10597, -0.10597, -0.10597, -0.10596]
df = pd.DataFrame([x, y, z, w], columns=['x', 'y', 'z', 'w'])
I created the following functions:
import math
def roll(qw, qx, qy, qz):
# x-axis rotation
sinr_cosp = +2.0 * (qw * qx + qy + qz)
cosr_cosp = +1.0 - 2.0 * (qx * qx + qy * qy)
roll = math.atan2(sinr_cosp, cosr_cosp)
return roll
def pitch(qw, qx, qy, qz):
# y-axis rotation
sinp = +2.0 * (qw * qy - qz * qx)
if(math.fabs(sinp) >= 1):
pitch = copysign(M_PI/2, sinp)
else:
pitch = math.asin(sinp)
return sinp
def yaw(qw, qx, qy, qz):
# z-axis rotation
siny_cosp = +2.0 * (qw * qz + qx * qy)
cosy_cosp = +1.0 - 2.0 * (qy * qy + qz * qz)
yaw = math.atan2(siny_cosp, cosy_cosp)
return yaw
Finally, using Pandas apply function, I tried to associate the result with a new column:
q_w = df['w']
q_x = df['x']
q_y = df['y']
q_z = df['z']
df['row'] = df.apply(roll(q_w, q_x, q_y, q_z))
The same error occurs when using the other functions.
I saw an issue right here on Stack where this bug was fixed using Numpy. I believe this is not possible here because I am using functions specific to the Math package.
TypeError Traceback (most recent call
last) /usr/local/lib/python3.6/dist-packages/pandas/core/series.py in
wrapper(self)
92 raise TypeError("cannot convert the series to "
---> 93 "{0}".format(str(converter)))
94
TypeError: cannot convert the series to
The above exception was the direct cause of the following exception:
SystemError Traceback (most recent call
last) 4 frames in ()
----> 1 df['row'] = df.apply(roll(q_w, q_x, q_y, q_z))
in roll(qw, qx, qy, qz)
4 sinr_cosp = +2.0 * (qw * qx + qy + qz)
5 cosr_cosp = +1.0 - 2.0 * (qx * qx + qy * qy)
----> 6 roll = math.atan2(sinr_cosp, cosr_cosp)
7 return roll
8
/usr/local/lib/python3.6/dist-packages/pandas/core/series.py in
wrapper(self)
88
89 def wrapper(self):
---> 90 if len(self) == 1:
91 return converter(self.iloc[0])
92 raise TypeError("cannot convert the series to "
/usr/local/lib/python3.6/dist-packages/pandas/core/series.py in
len(self)
593 Return the length of the Series.
594 """
--> 595 return len(self._data)
596
597 def view(self, dtype=None):
/usr/local/lib/python3.6/dist-packages/pandas/core/internals/managers.py
in len(self)
290
291 def len(self):
--> 292 return len(self.items)
293
294 def unicode(self):
SystemError: PyEval_EvalFrameEx returned a result with an error set

Answer 1

You should using apply like
df.apply(lambda x : roll(x['w'],x['x'],x['y'],x['z']),1)
Out[291]:
0 -2.175472
1 -1.909103
2 -0.394163
3 -0.397885
dtype: float64

Answer 2

You could also modify your function.
def roll(df):
# x-axis rotation
sinr_cosp = +2.0 * (df.w * df.x + df.y + df.z)
cosr_cosp = +1.0 - 2.0 * (df.x * df.x + df.y * df.y)
roll = math.atan2(sinr_cosp, cosr_cosp)
return roll
df.apply(roll, axis=1)
Out:
0 -2.175472
1 -1.909103
2 -0.394163
3 -0.397885
dtype: float64