dataFile.go

////////////////////////////////////////////////////////////////////////////////
//	dataFile.go  -  Sep-5-2022  -  aldebap
//
//	Parser for Go-Plot data files
////////////////////////////////////////////////////////////////////////////////

package plot

import (
	"bufio"
	"errors"
	"fmt"
	"strconv"
	"strings"
)

//	LoadDataFile load a data file and return a Plot
func LoadDataFile(x_column uint8, y_column uint8, reader *bufio.Reader) ([]Point_2d, error) {
	point := make([]Point_2d, 0, 10)

	//	read the input line by line
	var line string
	var firstLine = true

	for {
		bufLine, isPrefix, err := reader.ReadLine()
		if err != nil {
			break
		}

		line += string(bufLine)

		if !isPrefix {
			//	ignore first line since it's expected to be a header
			if firstLine {
				firstLine = false
				line = ""
				continue
			}

			line = strings.TrimLeft(line, " ")
			line = strings.TrimRight(line, " ")

			//	doing the split manually as strings.split() doesn't behave correctly when multiple spaces separate columns
			//column := strings.Split(line, " ")
			var column []string = make([]string, 0)
			var value string

			for _, char := range line {
				if char == ' ' {
					if len(value) > 0 {
						column = append(column, value)
						value = ""
					}
					continue
				}
				value = value + string(char)
			}
			if len(value) > 0 {
				column = append(column, value)
			}

			//	check if the line have the expected columns
			if len(column) < int(x_column) || len(column) < int(y_column) {
				return nil, errors.New(`line with less columns than expected: "` + line + `"`)
			}

			//	check if the columns are numeric
			x, err := strconv.ParseFloat(column[x_column-1], 64)
			if err != nil {
				return nil, errors.New(`column ` + fmt.Sprintf("%d", x_column) + ` expected to be numeric: "` + line + `"`)
			}

			y, err := strconv.ParseFloat(column[y_column-1], 64)
			if err != nil {
				return nil, errors.New(`column ` + fmt.Sprintf("%d", y_column) + ` expected to be numeric: "` + line + `"`)
			}

			//	add the new point
			point = append(point, Point_2d{X: x, Y: y})

			line = ""
		}
	}

	return point, nil
}