[Tutor] Parsing

[bob gailer]

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On 11/27/2011 3:45 PM, Deanna Wilson wrote:
> Project 4: Parsing rhinoceros sightings
>
> In this project, I'm  working for a wildlife conservation group that 
> is tracking rhinos in the African savannah. My  field workers' 
> software resources and GIS expertise are limited, but you have managed 
> to obtain an Excel spreadsheet 
> <https://www.e-education.psu.edu/drupal6/files/geog485py/data/RhinoObservations.xlsx> 
> showing the positions of several rhinos over time. Each record in the 
> spreadsheet shows the latitude/longitude coordinate of a rhino along 
> with the rhino's name (these rhinos are well known to your field workers).
>
> I want to write a script that will turn the readings in the 
> spreadsheet into a vector dataset that I can place on a map. This will 
> be a polyline dataset showing the tracks the rhinos followed over the 
> time the data was collected.
>
> I will deliver:
>
> A Python script that reads the data from the spreadsheet and creates, 
> from scratch, a polyline shapefile with n polylines, n being the 
> number of rhinos in the spreadsheet. Each polyline should represent a 
> rhino's track chronologically from the beginning of the spreadsheet to 
> the end of the spreadsheet. Each polyline should also have a text 
> attribute containing the rhino's name. The shapefile should use the 
> WGS 1984 geographic coordinate system.
>
> Challenges
>
> The data is in a format (XLSX) that you cannot easily parse. The first 
> step I must do is manually open the file in Excel and save it as a 
> comma-delimited format that I can easily read with a script. Choose 
> the option CSV (comma-delimited) (*.csv). I did this
>
>   * The rhinos in the spreadsheet appear in no guaranteed order, and
>     not all the rhinos appear at the beginning of the spreadsheet. As
>     I parse each line, I must determine which rhino the reading
>     belongs to and update that rhino's polyline track accordingly. I
>     am not allowed to sort the Rhino column in Excel before I export
>     to the CSV file. My script must be "smart" enough to work with an
>     unsorted spreadsheet in the order that the records appear.
>   * I do not immediately know how many rhinos are in the file or even
>     what their names are. Although I could visually comb the
>     spreadsheet for this information and hard-code each rhino's name,
>     your script is required to handle all the rhino names
>     programmatically. The idea is that I should be able to run this
>     script on a different file, possibly containing more rhinos,
>     without having to make many manual adjustments.
>
> sample of my code:
>
> import arcpy
>
> shapefile = "C:\\...shp"
>
> pointFilePath = "C:\\...csv"
>
> pointFile = open(pointFilePath, "r")
>
> lineOfText = pointFile.readline()
>
> dataPairList = lineOfText.split(",")
>
> def addVertex(lat, lon, array):
>
>     vertex = arcpy.CreateObject("Point")
>
>     vertex.X = lon
>
>     vertex.Y = lat
>
>     array.add(vertex)
>
> def addPolyline(cursor, array):
>
>    feature = cursor.newRow()
>
>    feature.shape = array
>
>    cursor.insertRow(feature)
>
>    array.removeAll()
>
> def rhinoName(Rhino, dictionary):
>
>     if rhinoName in rhinoDictionary:
>
>         dictionary[rhinoName].append([latValue, lonValueIndex])
>
>     if rhinoName not in dictionary:
>
>         dictionary[rhinoName] = []
>
>     else:
>
>         dictionary[rhinoName]= ([latValue, lonValue])
>
> latValueIndex = dataPairList.index("X")
>
> lonValueIndex = dataPairList.index("Y")
>
> vertexArray = arcpy.CreateObject("Array")
>
> for line in pointFile.readlines():
>
>     segmentedLine = line.split(",")
>
>     latValue = segmentedLine[latValueIndex]
>
>     lonValue = segmentedLine[lonValueIndex]
>
>     vertex = arcpy.CreateObject("Point")
>
>     vertex.X = lonValue
>
>     vertex.Y = latValue
>
>     vertexArray.add(vertex)
>
>     polylineArray.add(currentPoint)
>
> cursor = arcpy.InsertCursor(shapefile)
>
> row = cursor.newRow()
>
> row.Shape = vertexArray
>
> cursor.insertRow(row)
>
> del cursor
>
>
>
>
>
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-- 
Bob Gailer
919-636-4239
Chapel Hill NC

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