Scenario: Creating a bar chart from the input data
This scenario describes a Job that reads source data from a CSV file and transforms
the data into a bar chart showing a comparison of several large cities. The input file
is shown below:
|
1 2 3 4 5 6 7 |
City;Population(x1000);LandArea(km2);PopulationDensity(people/km2) Beijing;10233;1418;7620 Moscow;10452;1081;9644 Seoul;10422;605;17215 Tokyo;8731;617;14151 Jakarta;8490;664;12738 New York;8310;789;10452 |
Because the input file has a different structure than the one required by the
tBarChart component, this use case uses the
tMap component to adapt the source data to the
three-column schema of tBarChart so that a temporary
CSV file can be created as the input to the tBarChart
component.
You will usually use the tMap component to adjust
the input schema in accordance with the schema structure of the tBarChart component. For more information about how to
use the tMap component, see
Talend Studio User
Guide and tMap.
To ensure correct generation of the temporary input file, a pre-treatment subjob is
used to delete the temporary file in case it already exists before the main Job is
executed; as this temporary file serves this specific Job only, a post-treatment subjob
is used to deleted it after the main Job is executed.