curl --request POST \
  --url https://api.fincept.in/quantlib/numerical/linalg/lstsq \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "A": [
    [
      1,
      1
    ],
    [
      1,
      2
    ],
    [
      1,
      3
    ],
    [
      1,
      4
    ]
  ],
  "b": [
    2.1,
    2.9,
    4.2,
    4.9
  ]
}
'

import requests

url = "https://api.fincept.in/quantlib/numerical/linalg/lstsq"

payload = {
    "A": [[1, 1], [1, 2], [1, 3], [1, 4]],
    "b": [2.1, 2.9, 4.2, 4.9]
}
headers = {
    "X-API-Key": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'X-API-Key': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({A: [[1, 1], [1, 2], [1, 3], [1, 4]], b: [2.1, 2.9, 4.2, 4.9]})
};

fetch('https://api.fincept.in/quantlib/numerical/linalg/lstsq', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.fincept.in/quantlib/numerical/linalg/lstsq",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'A' => [
        [
                1,
                1
        ],
        [
                1,
                2
        ],
        [
                1,
                3
        ],
        [
                1,
                4
        ]
    ],
    'b' => [
        2.1,
        2.9,
        4.2,
        4.9
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-API-Key: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.fincept.in/quantlib/numerical/linalg/lstsq"

	payload := strings.NewReader("{\n  \"A\": [\n    [\n      1,\n      1\n    ],\n    [\n      1,\n      2\n    ],\n    [\n      1,\n      3\n    ],\n    [\n      1,\n      4\n    ]\n  ],\n  \"b\": [\n    2.1,\n    2.9,\n    4.2,\n    4.9\n  ]\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("X-API-Key", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.fincept.in/quantlib/numerical/linalg/lstsq")
  .header("X-API-Key", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"A\": [\n    [\n      1,\n      1\n    ],\n    [\n      1,\n      2\n    ],\n    [\n      1,\n      3\n    ],\n    [\n      1,\n      4\n    ]\n  ],\n  \"b\": [\n    2.1,\n    2.9,\n    4.2,\n    4.9\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.fincept.in/quantlib/numerical/linalg/lstsq")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["X-API-Key"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"A\": [\n    [\n      1,\n      1\n    ],\n    [\n      1,\n      2\n    ],\n    [\n      1,\n      3\n    ],\n    [\n      1,\n      4\n    ]\n  ],\n  \"b\": [\n    2.1,\n    2.9,\n    4.2,\n    4.9\n  ]\n}"

response = http.request(request)
puts response.read_body

{
  "success": true,
  "data": {
    "x": [
      1.02,
      0.94
    ]
  }
}

{
  "detail": "Invalid API key"
}

{
  "detail": "Endpoint requires Basic tier or higher"
}