curl --request POST \
  --url https://api.fincept.in/quantlib/numerical/interpolation/spline-derivative \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "x_data": [
    0,
    1,
    2,
    3
  ],
  "y_data": [
    0,
    1,
    4,
    9
  ],
  "xi": 1.5,
  "bc_type": "natural"
}
'

import requests

url = "https://api.fincept.in/quantlib/numerical/interpolation/spline-derivative"

payload = {
    "x_data": [0, 1, 2, 3],
    "y_data": [0, 1, 4, 9],
    "xi": 1.5,
    "bc_type": "natural"
}
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({x_data: [0, 1, 2, 3], y_data: [0, 1, 4, 9], xi: 1.5, bc_type: 'natural'})
};

fetch('https://api.fincept.in/quantlib/numerical/interpolation/spline-derivative', 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/interpolation/spline-derivative",
  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([
    'x_data' => [
        0,
        1,
        2,
        3
    ],
    'y_data' => [
        0,
        1,
        4,
        9
    ],
    'xi' => 1.5,
    'bc_type' => 'natural'
  ]),
  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/interpolation/spline-derivative"

	payload := strings.NewReader("{\n  \"x_data\": [\n    0,\n    1,\n    2,\n    3\n  ],\n  \"y_data\": [\n    0,\n    1,\n    4,\n    9\n  ],\n  \"xi\": 1.5,\n  \"bc_type\": \"natural\"\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/interpolation/spline-derivative")
  .header("X-API-Key", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"x_data\": [\n    0,\n    1,\n    2,\n    3\n  ],\n  \"y_data\": [\n    0,\n    1,\n    4,\n    9\n  ],\n  \"xi\": 1.5,\n  \"bc_type\": \"natural\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.fincept.in/quantlib/numerical/interpolation/spline-derivative")

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  \"x_data\": [\n    0,\n    1,\n    2,\n    3\n  ],\n  \"y_data\": [\n    0,\n    1,\n    4,\n    9\n  ],\n  \"xi\": 1.5,\n  \"bc_type\": \"natural\"\n}"

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

{
  "success": true,
  "data": {
    "xi": 1.5,
    "derivative": 3
  }
}

{
  "detail": "Invalid API key"
}

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