New mlr sparsify verb

docs/src/reference-verbs.md

@@ -3126,6 +3126,23 @@ a b c
 9 8 7
 </pre>
 
+## sparsify
+
+<pre class="pre-highlight-in-pair">
+<b>mlr sparsify --help</b>
+</pre>
+<pre class="pre-non-highlight-in-pair">
+Usage: mlr sparsify [options]
+Unsets fields for which the key is the empty string (or, optionally, another
+specified value). Only makes sense with output format not being CSV or TSV.
+Options:
+-s {filler string} What values to remove. Defaults to the empty string.
+-f {a,b,c} Specify field names to be operated on; any other fields won't be
+           modified. The default is to modify all fields.
+-h|--help  Show this message.
+Example: if input is a=1,b=,c=3 then output is a=1,c=3.
+</pre>
+
 ## split
 
 <pre class="pre-highlight-in-pair">
@@ -3409,14 +3426,14 @@ fields, optionally categorized by one or more fields.
 <b>  data/medium</b>
 </pre>
 <pre class="pre-non-highlight-in-pair">
-x_y_cov    0.000042574820827444476
-x_y_corr   0.0005042001844467462
-y_y_cov    0.08461122467974003
+x_y_cov    0.00004257482082749404
+x_y_corr   0.0005042001844473328
+y_y_cov    0.08461122467974005
 y_y_corr   1
-x2_xy_cov  0.04188382281779374
-x2_xy_corr 0.630174342037994
-x2_y2_cov  -0.00030953725962542085
-x2_y2_corr -0.0034249088761121966
+x2_xy_cov  0.041883822817793716
+x2_xy_corr 0.6301743420379936
+x2_y2_cov  -0.0003095372596253918
+x2_y2_corr -0.003424908876111875
 </pre>
 
 <pre class="pre-highlight-in-pair">
@@ -3425,12 +3442,12 @@ x2_y2_corr -0.0034249088761121966
 <b>  data/medium</b>
 </pre>
 <pre class="pre-non-highlight-in-pair">
-a   x_y_ols_m             x_y_ols_b           x_y_ols_n x_y_r2                  y_y_ols_m y_y_ols_b y_y_ols_n y_y_r2 xy_y2_ols_m        xy_y2_ols_b         xy_y2_ols_n xy_y2_r2
-pan 0.01702551273681908   0.5004028922897639  2081      0.00028691820445814767  1         0         2081      1      0.8781320866715662 0.11908230147563566 2081        0.41749827377311266
-eks 0.0407804923685586    0.48140207967651016 1965      0.0016461239223448587   1         0         1965      1      0.8978728611690183 0.10734054433612333 1965        0.45563223864254526
-wye -0.03915349075204814  0.5255096523974456  1966      0.0015051268704373607   1         0         1966      1      0.8538317334220835 0.1267454301662969  1966        0.38991721818599295
-zee 0.0027812364960399147 0.5043070448033061  2047      0.000007751652858786137 1         0         2047      1      0.8524439912011013 0.12401684308018937 2047        0.39356598090006495
-hat -0.018620577041095078 0.5179005397264935  1941      0.0003520036646055585   1         0         1941      1      0.8412305086345014 0.13557328318623216 1941        0.3687944261732265
+a   x_y_ols_m             x_y_ols_b          x_y_ols_n x_y_r2                  y_y_ols_m y_y_ols_b                           y_y_ols_n y_y_r2 xy_y2_ols_m        xy_y2_ols_b         xy_y2_ols_n xy_y2_r2
+pan 0.017025512736819345  0.500402892289764  2081      0.00028691820445815624  1         -0.00000000000000002890430283104539 2081      1      0.8781320866715664 0.11908230147563569 2081        0.4174982737731127
+eks 0.04078049236855813   0.4814020796765104 1965      0.0016461239223448218   1         0.00000000000000017862676354313703  1965      1      0.897872861169018  0.1073405443361234  1965        0.4556322386425451
+wye -0.03915349075204785  0.5255096523974457 1966      0.0015051268704373377   1         0.00000000000000004464425401127647  1966      1      0.8538317334220837 0.1267454301662969  1966        0.3899172181859931
+zee 0.0027812364960401333 0.5043070448033061 2047      0.000007751652858787357 1         0.00000000000000004819404567023685  2047      1      0.8524439912011011 0.12401684308018947 2047        0.39356598090006495
+hat -0.018620577041095272 0.5179005397264937 1941      0.00035200366460556604  1         -0.00000000000000003400445761787692 1941      1      0.8412305086345017 0.13557328318623207 1941        0.3687944261732266
 </pre>
 
 Here's an example simple line-fit. The `x` and `y`
@@ -3516,11 +3533,11 @@ upsec_count_pca_quality 0.9999590846136102
 donesec                 92.33051350964094
 
 color                   purple
-upsec_count_pca_m       -39.03009744795354
-upsec_count_pca_b       979.9883413064914
+upsec_count_pca_m       -39.030097447953594
+upsec_count_pca_b       979.9883413064917
 upsec_count_pca_n       21
 upsec_count_pca_quality 0.9999908956206317
-donesec                 25.10852919630297
+donesec                 25.108529196302943
 </pre>
 
 ## step
@@ -3797,9 +3814,9 @@ distinct_count 5      5      10000              10000                  10000
 mode           pan    wye    1                  0.3467901443380824     0.7268028627434533
 sum            0      0      50005000           4986.019681679581      5062.057444929905
 mean           -      -      5000.5             0.49860196816795804    0.5062057444929905
-stddev         -      -      2886.8956799071675 0.2902925151144007     0.290880086426933
-var            -      -      8334166.666666667  0.08426974433144456    0.08461122467974003
-skewness       -      -      0                  -0.0006899591185521965 -0.017849760120133784
+stddev         -      -      2886.8956799071675 0.29029251511440074    0.2908800864269331
+var            -      -      8334166.666666667  0.08426974433144457    0.08461122467974005
+skewness       -      -      0                  -0.0006899591185517494 -0.01784976012013298
 minlen         3      3      1                  15                     13
 maxlen         3      3      5                  22                     22
 min            eks    eks    1                  0.00004509679127584487 0.00008818962627266114

docs/src/reference-verbs.md.in

@@ -995,6 +995,12 @@ GENMD-RUN-COMMAND
 mlr --ijson --opprint sort-within-records data/sort-within-records.json
 GENMD-EOF
 
+## sparsify
+
+GENMD-RUN-COMMAND
+mlr sparsify --help
+GENMD-EOF
+
 ## split
 
 GENMD-RUN-COMMAND

pkg/transformers/aaa_transformer_table.go

@@ -62,6 +62,7 @@ var TRANSFORMER_LOOKUP_TABLE = []TransformerSetup{
 	SkipTrivialRecordsSetup,
 	SortSetup,
 	SortWithinRecordsSetup,
+	SparsifySetup,
 	SplitSetup,
 	SsubSetup,
 	Stats1Setup,

pkg/transformers/sparsify.go

@@ -0,0 +1,192 @@
+package transformers
+
+import (
+	"container/list"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/johnkerl/miller/pkg/cli"
+	"github.com/johnkerl/miller/pkg/lib"
+	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
+)
+
+// ----------------------------------------------------------------
+const verbNameSparsify = "sparsify"
+
+var SparsifySetup = TransformerSetup{
+	Verb:         verbNameSparsify,
+	UsageFunc:    transformerSparsifyUsage,
+	ParseCLIFunc: transformerSparsifyParseCLI,
+	IgnoresInput: false,
+}
+
+func transformerSparsifyUsage(
+	o *os.File,
+) {
+	fmt.Fprintf(o, "Usage: %s %s [options]\n", "mlr", verbNameSparsify)
+	fmt.Fprint(o,
+		`Unsets fields for which the key is the empty string (or, optionally, another
+specified value). Only makes sense with output format not being CSV or TSV.
+`)
+
+	fmt.Fprintf(o, "Options:\n")
+	fmt.Fprintf(o, "-s {filler string} What values to remove. Defaults to the empty string.\n")
+	fmt.Fprintf(o, "-f {a,b,c} Specify field names to be operated on; any other fields won't be\n")
+	fmt.Fprintf(o, "           modified. The default is to modify all fields.\n")
+	fmt.Fprintf(o, "-h|--help  Show this message.\n")
+
+	fmt.Fprint(o,
+		`Example: if input is a=1,b=,c=3 then output is a=1,c=3.
+`)
+}
+
+func transformerSparsifyParseCLI(
+	pargi *int,
+	argc int,
+	args []string,
+	_ *cli.TOptions,
+	doConstruct bool, // false for first pass of CLI-parse, true for second pass
+) IRecordTransformer {
+
+	// Skip the verb name from the current spot in the mlr command line
+	argi := *pargi
+	verb := args[argi]
+	argi++
+
+	fillerString := ""
+	var specifiedFieldNames []string = nil
+
+	for argi < argc /* variable increment: 1 or 2 depending on flag */ {
+		opt := args[argi]
+		if !strings.HasPrefix(opt, "-") {
+			break // No more flag options to process
+		}
+		if args[argi] == "--" {
+			break // All transformers must do this so main-flags can follow verb-flags
+		}
+		argi++
+
+		if opt == "-h" || opt == "--help" {
+			transformerSparsifyUsage(os.Stdout)
+			os.Exit(0)
+
+		} else if opt == "-s" {
+			fillerString = cli.VerbGetStringArgOrDie(verb, opt, args, &argi, argc)
+
+		} else if opt == "-f" {
+			specifiedFieldNames = cli.VerbGetStringArrayArgOrDie(verb, opt, args, &argi, argc)
+
+		} else {
+			transformerSparsifyUsage(os.Stderr)
+			os.Exit(1)
+		}
+	}
+
+	*pargi = argi
+	if !doConstruct { // All transformers must do this for main command-line parsing
+		return nil
+	}
+
+	transformer, err := NewTransformerSparsify(
+		fillerString,
+		specifiedFieldNames,
+	)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+
+	return transformer
+}
+
+// ----------------------------------------------------------------
+type TransformerSparsify struct {
+	fillerString          string
+	fieldNamesSet         map[string]bool
+	recordTransformerFunc RecordTransformerFunc
+}
+
+func NewTransformerSparsify(
+	fillerString string,
+	specifiedFieldNames []string,
+) (*TransformerSparsify, error) {
+
+	tr := &TransformerSparsify{
+		fillerString:  fillerString,
+		fieldNamesSet: lib.StringListToSet(specifiedFieldNames),
+	}
+	if specifiedFieldNames == nil {
+		tr.recordTransformerFunc = tr.transformAll
+	} else {
+		tr.recordTransformerFunc = tr.transformSome
+	}
+
+	return tr, nil
+}
+
+func (tr *TransformerSparsify) Transform(
+	inrecAndContext *types.RecordAndContext,
+	outputRecordsAndContexts *list.List, // list of *types.RecordAndContext
+	inputDownstreamDoneChannel <-chan bool,
+	outputDownstreamDoneChannel chan<- bool,
+) {
+	HandleDefaultDownstreamDone(inputDownstreamDoneChannel, outputDownstreamDoneChannel)
+
+	if !inrecAndContext.EndOfStream {
+		tr.recordTransformerFunc(
+			inrecAndContext,
+			outputRecordsAndContexts,
+			inputDownstreamDoneChannel,
+			outputDownstreamDoneChannel,
+		)
+	} else {
+		outputRecordsAndContexts.PushBack(inrecAndContext) // end-of-stream marker
+	}
+}
+
+func (tr *TransformerSparsify) transformAll(
+	inrecAndContext *types.RecordAndContext,
+	outputRecordsAndContexts *list.List, // list of *types.RecordAndContext
+	inputDownstreamDoneChannel <-chan bool,
+	outputDownstreamDoneChannel chan<- bool,
+) {
+	inrec := inrecAndContext.Record
+	outrec := mlrval.NewMlrmapAsRecord()
+
+	for pe := inrec.Head; pe != nil; pe = pe.Next {
+		if pe.Value.String() != tr.fillerString {
+			// Reference OK because ownership transfer
+			outrec.PutReference(pe.Key, pe.Value)
+		}
+	}
+
+	outrecAndContext := types.NewRecordAndContext(outrec, &inrecAndContext.Context)
+	outputRecordsAndContexts.PushBack(outrecAndContext)
+}
+
+// ----------------------------------------------------------------
+func (tr *TransformerSparsify) transformSome(
+	inrecAndContext *types.RecordAndContext,
+	outputRecordsAndContexts *list.List, // list of *types.RecordAndContext
+	inputDownstreamDoneChannel <-chan bool,
+	outputDownstreamDoneChannel chan<- bool,
+) {
+	inrec := inrecAndContext.Record
+	outrec := mlrval.NewMlrmapAsRecord()
+
+	for pe := inrec.Head; pe != nil; pe = pe.Next {
+		if tr.fieldNamesSet[pe.Key] {
+			if pe.Value.String() != tr.fillerString {
+				// Reference OK because ownership transfer
+				outrec.PutReference(pe.Key, pe.Value)
+			}
+		} else {
+			outrec.PutReference(pe.Key, pe.Value)
+		}
+	}
+
+	outrecAndContext := types.NewRecordAndContext(outrec, &inrecAndContext.Context)
+	outputRecordsAndContexts.PushBack(outrecAndContext)
+}

test/cases/cli-help/0001/expout

@@ -988,6 +988,18 @@ Options:
 -r        Recursively sort subobjects/submaps, e.g. for JSON input.
 -h|--help Show this message.
 
+================================================================
+sparsify
+Usage: mlr sparsify [options]
+Unsets fields for which the key is the empty string (or, optionally, another
+specified value). Only makes sense with output format not being CSV or TSV.
+Options:
+-s {filler string} What values to remove. Defaults to the empty string.
+-f {a,b,c} Specify field names to be operated on; any other fields won't be
+           modified. The default is to modify all fields.
+-h|--help  Show this message.
+Example: if input is a=1,b=,c=3 then output is a=1,c=3.
+
 ================================================================
 split
 Usage: mlr split [options] {filename}

test/cases/verb-sparsify/0001/cmd

@@ -0,0 +1 @@
+mlr --c2j --from test/input/sparsify-input.csv sparsify

test/cases/verb-sparsify/0001/expout

@@ -0,0 +1,17 @@
+[
+{
+  "a": 1,
+  "b": 2,
+  "c": 3
+},
+{
+  "a": 4,
+  "b": 5
+},
+{},
+{
+  "a": 7,
+  "b": 8,
+  "c": 9
+}
+]

test/cases/verb-sparsify/0002/cmd

@@ -0,0 +1 @@
+mlr --c2j --from test/input/sparsify-input.csv sparsify -f a

test/cases/verb-sparsify/0002/expout

@@ -0,0 +1,21 @@
+[
+{
+  "a": 1,
+  "b": 2,
+  "c": 3
+},
+{
+  "a": 4,
+  "b": 5,
+  "c": ""
+},
+{
+  "b": "",
+  "c": ""
+},
+{
+  "a": 7,
+  "b": 8,
+  "c": 9
+}
+]

test/cases/verb-sparsify/0003/cmd

@@ -0,0 +1 @@
+mlr --c2j --from test/input/sparsify-input.csv sparsify -f b

test/cases/verb-sparsify/0003/expout

@@ -0,0 +1,21 @@
+[
+{
+  "a": 1,
+  "b": 2,
+  "c": 3
+},
+{
+  "a": 4,
+  "b": 5,
+  "c": ""
+},
+{
+  "a": "",
+  "c": ""
+},
+{
+  "a": 7,
+  "b": 8,
+  "c": 9
+}
+]

test/cases/verb-sparsify/0004/cmd

@@ -0,0 +1 @@
+mlr --c2j --from test/input/sparsify-input.csv sparsify -f b,c