diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..76add87
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+node_modules
+dist
\ No newline at end of file
diff --git a/README.md b/README.md
index 125d80d..7d0f5b2 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,2 @@
-# math
-Mathematical algorithm
+# Math
+### Mathematical algorithm
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..52b98a8
--- /dev/null
+++ b/package.json
@@ -0,0 +1,9 @@
+{
+  "dependencies": {
+    "@types/node": "^14.11.10"
+  },
+  "scripts": {
+    "build":"tsc",
+    "dev":"tsc --watch"
+  }
+}
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..dcc3066
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,14 @@
+import median from "./lib/median";
+import average from "./lib/average";
+import leastSquareMethod from "./lib/least-square-method";
+import mode from "./lib/mode";
+import variance from "./lib/variance";
+import standardDeviation from "./lib/standard-deviation";
+export default {
+  median,
+  average,
+  leastSquareMethod,
+  mode,
+  variance,
+  standardDeviation
+}
\ No newline at end of file
diff --git a/src/lib/average.ts b/src/lib/average.ts
new file mode 100644
index 0000000..b1bccde
--- /dev/null
+++ b/src/lib/average.ts
@@ -0,0 +1,14 @@
+import sum from "./tools/sum";
+export default function average(list: list, weight?: list): number | null {
+  if (list.length >= 2) {
+    if (weight && weight.length === list.length) {
+      return sum(list.map((number, index) => number * weight[index])) / sum(weight);
+    } else {
+      return sum(list) / list.length;
+    }
+  } else if (list.length < 1) {
+    return null
+  } else {
+    return list[0];
+  }
+}
\ No newline at end of file
diff --git a/src/lib/least-square-method.ts b/src/lib/least-square-method.ts
new file mode 100644
index 0000000..17308bf
--- /dev/null
+++ b/src/lib/least-square-method.ts
@@ -0,0 +1,30 @@
+import average from "./average";
+interface res {
+  k: number | null
+  b: number | null
+}
+export default function leastSquareMethod(xyPair: xyList): res {
+  if (xyPair.length >= 2) {
+    let xs: list = [], ys: list = [], xys: list = [], xxs: list = [], averagedX: number, averagedY: number, averagedXY: number, averagedXX: number, k: number;
+    xyPair.forEach(xy => {
+      xs.push(xy.x);
+      ys.push(xy.y);
+      xys.push(xy.x * xy.y);
+      xxs.push(xy.x * xy.x);
+    });
+    averagedX = average(xs)!;
+    averagedY = average(ys)!;
+    averagedXY = average(xys)!;
+    averagedXX = average(xxs)!;
+    k = (averagedXY - averagedX * averagedY) / (averagedXX - averagedX * averagedX);
+    return {
+      k,
+      b: averagedY - averagedX * k
+    }
+  } else {
+    return {
+      k: null,
+      b: null
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/lib/median.ts b/src/lib/median.ts
new file mode 100644
index 0000000..e420da3
--- /dev/null
+++ b/src/lib/median.ts
@@ -0,0 +1,16 @@
+export default function median(list: list): number | null {
+  if (list.length > 0) {
+    let sortedList: list = list.sort();
+    if (sortedList.length < 2) {
+      return sortedList[0];
+    } else {
+      if (sortedList.length % 2 === 0) {
+        return (sortedList[sortedList.length / 2 - 1] + sortedList[sortedList.length / 2]) / 2;
+      } else {
+        return sortedList[Math.floor(sortedList.length / 2)]
+      }
+    }
+  } else {
+    return null
+  }
+}
\ No newline at end of file
diff --git a/src/lib/mode.ts b/src/lib/mode.ts
new file mode 100644
index 0000000..92f1c89
--- /dev/null
+++ b/src/lib/mode.ts
@@ -0,0 +1,16 @@
+import unique from "./tools/unique";
+interface xvPair {
+  n: number,
+  f: number
+}
+export default function mode(list: list): list | null {
+  if (list.length >= 2) {
+    let uniqueList: list = unique(list);
+    let valueList: list = uniqueList.map(number => list.join(' ').match(new RegExp(number.toString(), 'g'))!.length).map(v => Number(v));
+    return valueList.filter(v => v === Math.max(...valueList)).map(v => Number(uniqueList[valueList.indexOf(v)]));
+  } else if (list.length === 1) {
+    return [list[0]];
+  } else {
+    return null;
+  }
+}
\ No newline at end of file
diff --git a/src/lib/standard-deviation.ts b/src/lib/standard-deviation.ts
new file mode 100644
index 0000000..b714a96
--- /dev/null
+++ b/src/lib/standard-deviation.ts
@@ -0,0 +1,8 @@
+import variance from "./variance";
+export default function standardDeviation(list:list):number{
+  if(list.length > 1){
+    return Math.sqrt(variance(list));
+  }else{
+    return 0;
+  }
+}
\ No newline at end of file
diff --git a/src/lib/tools/sum.ts b/src/lib/tools/sum.ts
new file mode 100644
index 0000000..942aabc
--- /dev/null
+++ b/src/lib/tools/sum.ts
@@ -0,0 +1,13 @@
+export default function sum(list: list): number {
+  if (list.length < 1) {
+    return 0;
+  } else if (list.length < 2) {
+    return list[0];
+  } else {
+    let res = 0;
+    list.forEach(number => {
+      res += number
+    });
+    return res;
+  }
+}
\ No newline at end of file
diff --git a/src/lib/tools/unique.ts b/src/lib/tools/unique.ts
new file mode 100644
index 0000000..1848758
--- /dev/null
+++ b/src/lib/tools/unique.ts
@@ -0,0 +1,7 @@
+export default function unique(list: list): list {
+  if (list.length > 1) {
+    return [...(new Set(list))];
+  } else {
+    return list;
+  }
+}
\ No newline at end of file
diff --git a/src/lib/variance.ts b/src/lib/variance.ts
new file mode 100644
index 0000000..74ce35a
--- /dev/null
+++ b/src/lib/variance.ts
@@ -0,0 +1,9 @@
+import average from "./average";
+import sum from "./tools/sum";
+export default function variance(list:list):number{
+  if(list.length > 1){
+    return sum(list.map(number=>Math.pow(number - average(list)!,2))) / list.length;
+  }else{
+    return 0;
+  }
+}
\ No newline at end of file
diff --git a/src/test/index.ts b/src/test/index.ts
new file mode 100644
index 0000000..0370aa3
--- /dev/null
+++ b/src/test/index.ts
@@ -0,0 +1,8 @@
+import math from "../index";
+console.log('start tests...')
+console.assert(math.median([1, 2, 3]) === 2, "check median");
+console.assert(math.average([1, 2, 3], [3, 2, 1]) === 10 / 6,"check weight average");
+console.assert(math.mode([2,4,4,3,3,3])!.toString() === [3].toString(),"check mode");
+console.assert(math.variance([1,2]) === (Math.pow(1-1.5,2)+Math.pow(2-1.5,2))/2,"check variance");
+console.assert(math.standardDeviation([1,2]) === Math.sqrt((Math.pow(1-1.5,2)+Math.pow(2-1.5,2))/2),"check standard deviation")
+console.log('all done');
\ No newline at end of file
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..5c04666
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,70 @@
+{
+  "typeAcquisition": {
+    "enable": false
+  },
+  "include": [
+    "src/**/*",
+    "types/**/*"
+  ],
+  "compilerOptions": {
+    /* Visit https://aka.ms/tsconfig.json to read more about this file */
+    /* Basic Options */
+    "incremental": true, /* Enable incremental compilation */
+    "target": "ES5", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
+    "module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
+    // "lib": [],                             /* Specify library files to be included in the compilation. */
+    "allowJs": true, /* Allow javascript files to be compiled. */
+    "checkJs": true, /* Report errors in .js files. */
+    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
+    // "declaration": true, /* Generates corresponding '.d.ts' file. */
+    // "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    // "sourceMap": true, /* Generates corresponding '.map' file. */
+    //"outFile": "./",                       /* Concatenate and emit output to single file. */
+    "outDir": "dist", /* Redirect output structure to the directory. */
+    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    "composite": true, /* Enable project compilation */
+    // "tsBuildInfoFile": "./BUILDINFO", /* Specify file to store incremental compilation information */
+    "removeComments": true, /* Do not emit comments to output. */
+    "suppressImplicitAnyIndexErrors": true,
+    // "noEmit": true,                        /* Do not emit outputs. */
+    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
+    "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+    /* Strict Type-Checking Options */
+    "strict": true, /* Enable all strict type-checking options. */
+    "noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
+    "strictNullChecks": true, /* Enable strict null checks. */
+    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
+    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
+    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
+    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
+    /* Additional Checks */
+    // "noUnusedLocals": true,                /* Report errors on unused locals. */
+    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
+    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
+    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */
+    /* Module Resolution Options */
+    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
+    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                       /* List of folders to include type definitions from. */
+    // "types": ["types/*.d.ts"],                    /* Type declaration files to be included in compilation. */
+    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    "esModuleInterop": true, /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
+    // "allowUmdGlobalAccess": true,          /* Allow accessing UMD globals from modules. */
+    /* Source Map Options */
+    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+    /* Experimental Options */
+    "experimentalDecorators": true, /* Enables experimental support for ES7 decorators. */
+    "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
+    /* Advanced Options */
+    "skipLibCheck": true, /* Skip type checking of declaration files. */
+    "forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the same file. */
+  }
+}
\ No newline at end of file
diff --git a/types/list.d.ts b/types/list.d.ts
new file mode 100644
index 0000000..a51a37a
--- /dev/null
+++ b/types/list.d.ts
@@ -0,0 +1 @@
+declare type list = number[];
\ No newline at end of file
diff --git a/types/xyList.d.ts b/types/xyList.d.ts
new file mode 100644
index 0000000..e00757f
--- /dev/null
+++ b/types/xyList.d.ts
@@ -0,0 +1,6 @@
+interface xyPair{
+  x:number
+  y:number
+}
+
+declare type xyList = xyPair[];
\ No newline at end of file
diff --git a/yarn.lock b/yarn.lock
new file mode 100644
index 0000000..7df5bb7
--- /dev/null
+++ b/yarn.lock
@@ -0,0 +1,8 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+"@types/node@^14.11.10":
+  version "14.11.10"
+  resolved "https://registry.npm.taobao.org/@types/node/download/@types/node-14.11.10.tgz?cache=0&sync_timestamp=1602874323764&other_urls=https%3A%2F%2Fregistry.npm.taobao.org%2F%40types%2Fnode%2Fdownload%2F%40types%2Fnode-14.11.10.tgz#8c102aba13bf5253f35146affbf8b26275069bef"
+  integrity sha1-jBAquhO/UlPzUUav+/iyYnUGm+8=