/// <summary>
/// If any column names in <param name="colNames" /> are present in <param name="input" />, this
/// method will create a transform that copies them to temporary columns. It will populate <param name="hiddenNames" />
/// with an array of string pairs containing the original name and the generated temporary column name, respectively.
/// </summary>
/// <param name="env"></param>
private static IDataView AliasIfNeeded(IHostEnvironment env, IDataView input, string[] colNames, out KeyValuePair <string, string>[] hiddenNames)
{
hiddenNames = null;
var toHide = new List <string>(colNames.Length);
foreach (var name in colNames)
{
int discard;
if (input.Schema.TryGetColumnIndex(name, out discard))
{
toHide.Add(name);
}
}
if (toHide.Count == 0)
{
return(input);
}
hiddenNames = toHide.Select(colName =>
new KeyValuePair <string, string>(colName, input.Schema.GetTempColumnName(colName))).ToArray();
return(ColumnCopyingTransformer.Create(env, new ColumnCopyingTransformer.Arguments()
{
Column = hiddenNames.Select(pair => new ColumnCopyingTransformer.Column()
{
Name = pair.Value, Source = pair.Key
}).ToArray()
}, input));
}
public static CommonOutputs.TransformOutput CopyColumns(IHostEnvironment env, ColumnCopyingTransformer.Arguments input)
{
Contracts.CheckValue(env, nameof(env));
var host = env.Register("CopyColumns");
host.CheckValue(input, nameof(input));
EntryPointUtils.CheckInputArgs(host, input);
var xf = ColumnCopyingTransformer.Create(env, input, input.Data);
return(new CommonOutputs.TransformOutput {
Model = new TransformModelImpl(env, xf, input.Data), OutputData = xf
});
}
private static IDataView UnaliasIfNeeded(IHostEnvironment env, IDataView input, KeyValuePair <string, string>[] hiddenNames)
{
if (Utils.Size(hiddenNames) == 0)
{
return(input);
}
input = ColumnCopyingTransformer.Create(env, new ColumnCopyingTransformer.Arguments()
{
Column = hiddenNames.Select(pair => new ColumnCopyingTransformer.Column()
{
Name = pair.Key, Source = pair.Value
}).ToArray()
}, input);
return(ColumnSelectingTransformer.CreateDrop(env, input, hiddenNames.Select(pair => pair.Value).ToArray()));
}
