Adding a row of strings ( header name ) to a array in python

Question

I have a data logging result.

I want to add / append names in the top of them in other words row wise i want to add names in 1st row of an array.

Like

Timestamp Accleration(x) Accleration(y) Accleration(z) Gyro(x) Gyro(y)

125252 ............ 12 ............ 10 ........ ...... 08 ................. 32 ............. 12

ANY HELP

    timestamped_imu_readings = np.ndarray((0,), np.float32)
    #creating and assigning an array to store readings
    timestamp= time.time()*1000
    #millisecond timestamping

    timestamped_imu_readings = np.append(timestamped_imu_readings, lsm6ds33.get_accelerometer_g_forces())
    timestamped_imu_readings = np.append(timestamped_imu_readings, lsm6ds33.get_accelerometer_angles())
    timestamped_imu_readings = np.append(timestamped_imu_readings, lsm6ds33.get_gyroscope_raw())
    timestamped_imu_readings = np.append(timestamped_imu_readings, lis3mdl.get_magnetometer_raw())
    #appending IMU readings to the array


    timestamped_imu_readings = np.append(float(timestamp),timestamped_imu_readings)
    #adding sensor readings in a row

    with open("IMU_Readings_muh.csv", "ab") as f:
    np.savetxt(f, np.expand_dims(timestamped_imu_readings, axis=0),  fmt="%4.8f" , delimiter=",")

So basically what we have is a list of lists like this [[data_row1],[data_row2],[data_row..]] And you want something like this: [[names],[data_row1],[data_row2],[data_row..]]. Is that correct ? — Shadesfear
– Shadesfear, Commented Aug 30, 2019 at 13:00
@Shadesfear yes, [[title_1],[data_column1]] ,[[title_2],[data_column_2]], [[title_3],[data_column_3]] but i cannot use header in numpy.savetext because it runs inside while loop and it creates header names for each entry. appending may be !!! — rajy
– rajy, Commented Sep 2, 2019 at 8:27
@hpaulj but i cannot use header in numpy.savetext because in my code savetext runs inside while loop and it creates header names for each entry. appending may be !!! — rajy
– rajy, Commented Sep 2, 2019 at 8:29
savetxt is just a bunch of formatted f.write. If you don't like what it writes, write your own. There's no compiled magic. — hpaulj
– hpaulj, Commented Sep 2, 2019 at 10:47

Shadesfear · Accepted Answer · 2019-09-02 11:55:04Z

Take a look at the following snippet, we define the array as a list of lists with the column names as the first element in the list.

Then we concatenate with the "data" rows, line by line, that are represented with np.ones() in this example

import numpy as np

a = np.array([["title_1", "title_2", "title_3", "title_4", "title_5"]])
a = np.concatenate((a, [np.ones(5)]))
a = np.concatenate((a, [np.ones(5)*2]))
a = np.concatenate((a, [np.ones(5)*3]))
print(a)

This produces output like this

[['title_1' 'title_2' 'title_3' 'title_4' 'title_5']
 ['1.0' '1.0' '1.0' '1.0' '1.0']
 ['2.0' '2.0' '2.0' '2.0' '2.0']
 ['3.0' '3.0' '3.0' '3.0' '3.0']]

If we dont have the names before getting the data, we just reverse the order.

b = np.array([np.ones(5)])
b = np.concatenate((b, [np.ones(5)*2]))
b = np.concatenate((b, [np.ones(5)*3]))

names = np.array([["title_1", "title_2", "title_3", "title_4", "title_5"]])
names = np.concatenate((names, b))

print(names)

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