fixed tests and updated docs

Author: Jolanrensen

core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/Access.kt

@@ -630,6 +630,7 @@ class Access : TestBase() {
         df.select { age and name }
         df.fillNaNs { dfsOf<Double>() }.withZero()
         df.remove { cols { it.hasNulls() } }
+        df.group { cols { it.data != name } }.into { "nameless" }
         df.update { city }.notNull { it.lowercase() }
         df.gather { colsOf<Number>() }.into("key", "value")
         df.move { name.firstName and name.lastName }.after { city }
@@ -790,6 +791,7 @@ class Access : TestBase() {
 
     @Test
     fun columnSelectorsMisc() {
+        val df = df.add { "year" from { 0 } }
         // SampleStart
         // by condition
         df.select { cols { it.name().startsWith("year") } }
@@ -813,7 +815,7 @@ class Access : TestBase() {
         df.select { dropLast(2) }
 
         // find the first column satisfying the condition
-        df.select { first { it.name().startsWith("year") } }
+        df.select { first { it.name.startsWith("year") } }
 
         // find the last column inside a column group satisfying the condition
         df.select {

core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataFrameTests.kt

@@ -1395,7 +1395,7 @@ class DataFrameTests : BaseTest() {
             ).toDataFrame().cast<Person>()
             res shouldBe typed
         }
-        typed.group { cols { it != name } }.into { it.type.jvmErasure.simpleName!! }.check()
+        typed.group { cols { it.data != name } }.into { it.type.jvmErasure.simpleName!! }.check()
         typed.group { age and city and weight }.into { it.type.jvmErasure.simpleName!! }.check()
     }
 

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/Access.kt

@@ -630,6 +630,7 @@ class Access : TestBase() {
         df.select { age and name }
         df.fillNaNs { dfsOf<Double>() }.withZero()
         df.remove { cols { it.hasNulls() } }
+        df.group { cols { it.data != name } }.into { "nameless" }
         df.update { city }.notNull { it.lowercase() }
         df.gather { colsOf<Number>() }.into("key", "value")
         df.move { name.firstName and name.lastName }.after { city }
@@ -790,6 +791,7 @@ class Access : TestBase() {
 
     @Test
     fun columnSelectorsMisc() {
+        val df = df.add { "year" from { 0 } }
         // SampleStart
         // by condition
         df.select { cols { it.name().startsWith("year") } }
@@ -813,7 +815,7 @@ class Access : TestBase() {
         df.select { dropLast(2) }
 
         // find the first column satisfying the condition
-        df.select { first { it.name().startsWith("year") } }
+        df.select { first { it.name.startsWith("year") } }
 
         // find the last column inside a column group satisfying the condition
         df.select {

core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataFrameTests.kt

@@ -1395,7 +1395,7 @@ class DataFrameTests : BaseTest() {
             ).toDataFrame().cast<Person>()
             res shouldBe typed
         }
-        typed.group { cols { it != name } }.into { it.type.jvmErasure.simpleName!! }.check()
+        typed.group { cols { it.data != name } }.into { it.type.jvmErasure.simpleName!! }.check()
         typed.group { age and city and weight }.into { it.type.jvmErasure.simpleName!! }.check()
     }
 

docs/StardustDocs/topics/ColumnSelectors.md

@@ -12,6 +12,7 @@ Column selectors are used in many operations:
 df.select { age and name }
 df.fillNaNs { dfsOf<Double>() }.withZero()
 df.remove { cols { it.hasNulls() } }
+df.group { cols { it.data != name } }.into { "nameless" }
 df.update { city }.notNull { it.lowercase() }
 df.gather { colsOf<Number>() }.into("key", "value")
 df.move { name.firstName and name.lastName }.after { city }
@@ -207,7 +208,7 @@ df.select { drop(2) }
 df.select { dropLast(2) }
 
 // find the first column satisfying the condition
-df.select { first { it.name().startsWith("year") } }
+df.select { first { it.name.startsWith("year") } }
 
 // find the last column inside a column group satisfying the condition
 df.select {