# Documentation

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# isdouble

Determine if digital filter coefficients are double precision

## Syntax

``````flag = isdouble(d)``````

## Description

example

``````flag = isdouble(d)``` returns `true` if the coefficients of a digital filter, `d`, are double precision.```

## Examples

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Use `designfilt` to design a sixth-order highpass IIR filter. Specify a normalized passband frequency of rad/sample. Convert it to a single-precision filter. Identify the precision in each case.

```fd = designfilt('highpassiir','FilterOrder',6,'PassbandFrequency',0.6); isd = isdouble(fd)```
```isd = logical 1 ```
```fs = single(fd); iss = isdouble(fs)```
```iss = logical 0 ```

## Input Arguments

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Digital filter, specified as a `digitalFilter` object. Use `designfilt` to generate `d`. If you want a single-precision filter, apply `single` to the output of `designfilt`.

Example: `d = designfilt('lowpassiir','FilterOrder',3,'HalfPowerFrequency',0.5)` specifies a third-order Butterworth filter with normalized 3-dB frequency 0.5π rad/sample.

## Output Arguments

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Type identification, returned as a logical scalar.

## See Also

#### Introduced in R2014a

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