npm package: @stdlib/math-base-special-truncsd
Description: Round a numeric value to the nearest number toward zero with N significant figures.
Author: The Stdlib Authors
Latest version: 0.3.1

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# truncsd

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> Round a numeric value to the nearest number toward zero with `n` significant figures.

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-truncsd
```

</section>

<section class="usage">

## Usage

```javascript
var truncsd = require( '@stdlib/math-base-special-truncsd' );
```

#### truncsd( x, n, b )

Rounds a `numeric` value to the nearest `number` toward zero with `n` significant figures.

```javascript
var v = truncsd( 3.141592653589793, 5, 10 );
// returns 3.1415

v = truncsd( 3.141592653589793, 1, 10 );
// returns 3.0

v = truncsd( 12368.0, 2, 10 );
// returns 12000.0

v = truncsd( 0.0313, 2, 2 );
// returns 0.03125
```

</section>

<!-- /.usage -->

<section class="notes">

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var truncsd = require( '@stdlib/math-base-special-truncsd' );

var opts = {
    'dtype': 'float64'
};
var x = uniform( 100, -5000.0, 5000.0, opts );

logEachMap( 'x: %0.4f. a: %d. b: %d. Rounded: %0.4f.', x, 5, 10, truncsd );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/truncsd.h"
```

#### stdlib_base_truncsd( x, n, b )

Rounds a `numeric` value to the nearest `number` toward negative infinity with `n` significant figures.

```c
double out = stdlib_base_truncsd( 3.141592653589793, 5, 10 );
// returns 3.1415
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.
-   **n**: `[in] int32_t` number of significant figures.
-   **b**: `[in] int32_t` base.

```c
double stdlib_base_truncsd( const double x, const int32_t n, const int32_t b );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/math/base/special/truncsd.h"
#include <stdio.h>
#include <stdint.h>

int main( void ) {
    const double x[] = { -5.0, -3.89, -2.78, -1.67, -0.56, 0.56, 1.67, 2.78, 3.89, 5.0 };
    const int32_t n[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    const int32_t b[] = { 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 };

    double v;
    int i;
    for ( i = 0; i < 10; i++ ) {
        v = stdlib_base_truncsd( x[ i ], n[ i ], b[ i ] );
        printf( "truncsd(%lf, %d, %d) = %lf\n", x[ i ], n[ i ], b[ i ], v );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math-base/special/ceilsd`][@stdlib/math/base/special/ceilsd]</span><span class="delimiter">: </span><span class="description">round a numeric value to the nearest number toward positive infinity with N significant figures.</span>
-   <span class="package-name">[`@stdlib/math-base/special/floorsd`][@stdlib/math/base/special/floorsd]</span><span class="delimiter">: </span><span class="description">round a numeric value to the nearest number toward negative infinity with N significant figures.</span>
-   <span class="package-name">[`@stdlib/math-base/special/roundsd`][@stdlib/math/base/special/roundsd]</span><span class="delimiter">: </span><span class="description">round a double-precision floating-point number to the nearest value with N significant figures.</span>
-   <span class="package-name">[`@stdlib/math-base/special/trunc`][@stdlib/math/base/special/trunc]</span><span class="delimiter">: </span><span class="description">round a double-precision floating-point number toward zero.</span>

</section>

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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[@stdlib/math/base/special/ceilsd]: https://www.npmjs.com/package/@stdlib/math-base-special-ceilsd

[@stdlib/math/base/special/floorsd]: https://www.npmjs.com/package/@stdlib/math-base-special-floorsd

[@stdlib/math/base/special/roundsd]: https://www.npmjs.com/package/@stdlib/math-base-special-roundsd

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