detectImportOptions

Create import options based on file content.

📝Syntax

options = detectImportOptions(filename)
options = detectImportOptions(filename, Name, Value)

📥Input Arguments

Parameter	Description
filename	a string: filename source.
Name, Value	JSON files only: FileType, TableSelector, TableNodeName, VariableSelectors, RowNamesSelector, VariableUnitsSelector, VariableDescriptionsSelector, RepeatedNodeRule, ParsingMode, AllowComments, AllowInfAndNaN, AllowTrailingCommas, MissingRule, ImportErrorRule and TextType (see readtable).

📤Output Arguments

Parameter	Description
options	nelson.io.text.DelimitedTextImportOptions object.

📄Description

options = detectImportOptions(filename) identifies a table in a delimited text file and returns a nelson.io.text.DelimitedTextImportOptions object.

You can customize this object and use it withreadtable, readcell orreadmatrix to control how Nelson imports data as a table, cell array, or matrix.

Properties:

Delimiter: Field delimiter characters. example: {','}

LineEnding: End-of-line characters. example: {'\r\n'}

CommentStyle: Style of comments. example: {'#'}

EmptyLineRule: Procedure to handle empty lines. example: 'skip'

VariableNamesLine: Variable names location. example: 1

VariableNames: Variable names. example: {'Names' 'Age' 'Height' 'Weight'}

RowNamesColumn: Row names location. example: 0

DataLines: Data location, [l1 l2] Indicate the range of lines containing the data. l1 refers to the first line with data, while l2 refers to the last line. example: [2 Inf]

For a JSON file (.json extension or 'FileType', 'json'), detectImportOptions returns a nelson.io.json.JSONImportOptions object usable with readtable and readtimetable. Its TableSelector and VariableSelectors properties hold the detected JSON Pointers, VariableNames and VariableTypes the detected names and types.

💡Examples

  Names = {'John'; 'Alice'; 'Bob'; 'Diana'};  Age = [28; 34; 22; 30];  Height = [175; 160; 180; 165];  Weight = [70; 55; 80; 60];  T = table(Names, Age, Height, Weight);  writetable(T, [tempdir,'readcell_1.csv'])  options = detectImportOptions([tempdir,'readcell_1.csv'])  C1 = readcell([tempdir,'readcell_1.csv'], options)  options.DataLines = [1 Inf]  C2 = readcell([tempdir,'readcell_1.csv'], options)

Detect the options of a JSON file:

T = table([1; 2], ["a"; "b"], 'VariableNames', {'x', 'name'}); f = [tempdir, 'detect_json.json']; writetable(T, f); opts = detectImportOptions(f) opts.SelectedVariableNames = {'name'}; T2 = readtable(f, opts)

🕔Version History

Version	Description
1.10.0	initial version
2.0.0	JSON files: returns a JSONImportOptions object.