How to declare floating numbers, assuming this is the problem

Processing.py
1

I have errors with the following PyProcessing code below.

  1. The first error I get is
    TypeError: can’t multiply sequence by non-int of type ‘float’
    on the line 'v_lat=v_lat*0.0174533 ’

I think this is due to v_lat being a string and needs to be converted to a floating number.

  1. So I changed ‘v_lat=row[1]’ to ‘v_lat=float(row[1])’ and I get this error
    ‘ValueError: invalid literal for float: Latitude’

Appreciate any help/tips with how I can convert string to floating number, assuming this is the cause of the problem. Thanks.

PyProcessing code is:

convert latitude and longitude values to x,y,z co-ordinates

import csv
c_csvfile=‘latlon1.csv’
c_eradius=6378.147 # earth radius, used with lat and lon to calc x y z coordinates
c_radian=0.0174533 # pi/180

def setup():
size(500,500)
background(255)

statsFileHandle=open(c_csvfile)
statsData=csv.reader(statsFileHandle)
for row in statsData:
    v_time=row[0]
    v_lat=row[1]
    v_lon=row[2]

convert to radians

    v_lat=v_lat*0.0174533 
    v_lon=v_lon*0.0174533

#convert to x,y,z
v_x=c_eradius*cos(v_lat)cos(v_lon)
v_y=c_eradiuscos(v_lat)sin(v_lon)
v_z=c_eradiussin(v_lat)

    print(str(v_time)+" : "+str(v_lat)+" : "+str(v_lon))

latlon1.csv file has these values:

Time Latitude Longitude
2021-06-23 21:41:57 -34.0459032 151.1109382
2021-06-23 21:42:00 -34.0459232 151.1109829
2021-06-23 21:42:04 -34.0460907 151.1113508
2021-06-23 21:42:08 -34.0461909 151.1115345
2021-06-23 21:42:15 -34.0461581 151.1113933
2021-06-23 21:42:19 -34.0461696 151.1113905
2021-06-23 21:42:29 -34.0461639 151.1114605
2021-06-23 21:42:37 -34.0461209 151.1114227
2021-06-23 21:42:38 -34.0461209 151.1114227
1 Like
2

Your “latlon1.csv” file has a title header for its 3 column names.

Obviously neither “Latitude” nor “Longitude” can be converted to a float().

I’m not well versed on Python’s builtin library so I had to look up on how to use its csv module.

This is what I’ve come up w/. However I haven’t tested it at all. Use it at your own risk:

    global coords
    coords = []

    with open('latlon1.csv') as csvFile:
        # Sniff 1st 256 bytes of file for header presence:
        hasHeader = csv.Sniffer().has_header(csvFile.read(256))
        csvFile.seek(0) # go back to begining of file after the sniff read

        csvReader = csv.reader(csvFile)

        if hasHeader:
            header = next(csvReader) # trick to skip CSV header
            print header

        for row in csvReader: # file safe to iterate now
            stamp = row[0]
            lat = radians(float(row[1]))
            lon = radians(float(row[2]))

            print stamp, lat, lon

            coords.append((stamp, lat, lon))

Although mysteriously absent in Python Mode’s web reference:

You should take a look on Processing’s loadTable(), which forum members here are more familiar w/:

3 Likes
3

Thanks @GoToLoop
Yes, thanks for highlighting that the error refers to the heading line.
I have been caught before with this heading line thing…
I thought it was looking at the values rows and that it was referring the value as a string and somehow it knows that it was of latitude format, so I tried to convert it to a float.

So after skipping the first row, the sketch works as expected.
Cheers

2 Likes
4

@GoToLoop
so I skipped first row by creating and checking an on/off boolean variable for first row, so as not to process this first row.
I also used the radians function as you have suggested above instead of calculating it ‘manually’
Thanks

5

You can also multiply by DEG_TO_RAD for the same effect:
lat = radians(float(row[1])) → lat = float(row[1]) * DEG_TO_RAD

Didn’t next() work for you? next(csvReader)

Placing a check inside a loop makes it more complex & slow IMO.

Alternatively you can turn the csv.reader() into a list() or tuple() and then slice its 1st element: [1:]

global coords
coords = []

with open('latlon1.csv') as csvFile:
    for row in tuple(csv.reader(csvFile))[1:]: # skips 1st header row
        stamp = row[0]
        lat = float(row[1]) * DEG_TO_RAD
        lon = float(row[2]) * DEG_TO_RAD

        print stamp, lat, lon

        coords.append((stamp, lat, lon))
3 Likes
6

Thank you for the above, suggestions noted and will test them out. Cheers.