GetChart: Make request to Zillow API GetChart Web Service
In xiyuansun/realEstAnalytics: Interfacing with Zillow's API in R

Description Usage Arguments Value Examples

The GetChart API generates a URL for an image file that displays historical Zestimates for a specific property. The API accepts as input the Zillow Property ID as well as a chart type: either percentage or dollar value change. Optionally, the API accepts width and height parameters that constrain the size of the image. The historical data can be for the past 1 year, 5 years or 10 years.

GetChart(zpid = NULL, unit_type = c("percent", "dollar"),
  width = NULL, height = NULL, chartDuration = c("1year", "5years",
  "10years"), zws_id = NULL,
  url = "http://www.zillow.com/webservice/GetChart.htm")

`zpid`	The Zillow Property ID for the property for which to obtain information. Required.
`unit_type`	A string value that specifies whether to show the percent change (unit_type = 'percent') or dollar change (unit_type = 'dollar'). Required.
`width`	An integer value that specifies the width of the generated image; the value must be between 200 and 600, inclusive.
`height`	An integer value that specifies the height of the generated image; the value must be between 100 and 300, inclusive.
`chartDuration`	The duration of past data that needs to be shown in the chart. Valid values are '1year', '5years' and '10years'. If unspecified, the value defaults to '1year'.
`zws_id`	The Zillow Web Service Identifier. Required.
`url`	URL for the GetChart Web Service. Required.

A named list with the following elements:

request: a list with the request parameters
message: a list of status code(s) and message(s) returned by the API
response: an XMLNode with the API-specific response values. At this time, no further coercion is performed, so you may have to use functions from the XML package to extract the desired output.

## Not run: 
GetChart(zpid = 1340244, unit_type = 'dollar', width = 600, height = 300,
 chartDuration = '10years', zws_id = getOption('ZillowR-zws_id'))

GetChart(zpid = 1340244, unit_type = 'percent', width = 800, height = 400,
chartDuration = '5years', zws_id = getOption('ZillowR-zws_id'))

## End(Not run)