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package dstream
import "fmt"
type drop struct {
xform
dropVars []string
keepPos []int
}
func (d *drop) init() {
// Check that all variables to drop exist.
hna := make(map[string]bool)
for _, v := range d.source.Names() {
hna[v] = true
}
dmp := make(map[string]bool)
for _, na := range d.dropVars {
if !hna[na] {
msg := fmt.Sprintf("Drop: variable '%s' not found.\n", na)
panic(msg)
}
dmp[na] = true
}
for k, na := range d.source.Names() {
if !dmp[na] {
d.keepPos = append(d.keepPos, k)
d.names = append(d.names, na)
}
}
d.bdata = make([]interface{}, len(d.keepPos))
}
// DropCols removes the given variables from a Dstream.
func DropCols(data Dstream, dropvars ...string) Dstream {
d := &drop{
xform: xform{
source: data,
},
dropVars: dropvars,
}
d.init()
return d
}
func (d *drop) Next() bool {
if !d.source.Next() {
return false
}
for j, k := range d.keepPos {
d.bdata[j] = d.source.GetPos(k)
}
return true
}
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