Math and Filtering Functions

Analyse-Plus has a very large and complete library of functions to assist in analysis of data. Filter functions are among those used the most. RC filters emulate those used in control systems so you can simulate their effect before implementing them in your control. You can also approximate mixing in a mix tank for simulation purposes. In most cases, the filters can be used as low pass, high pass, band pass or band reject filters.















To use math functions, you select up to 10 source data files from the Quick List of opened files. Then use the Function Select button to choose the function category, then click on the individual function. A pop-up box will appear with the parameters to be entered like a form. Fill these in, click OK and the resulting function appears in the Current Formula box. You can directly enter these and copy/paste them. You can also select a past one from the Formula History. You can create complex and concise operations with up to 14 levels of brackets. Then enter the Destination File name (a new or existing filename).

Filter Functions

Functions ending in “f” allow entering the cut-off frequency as the main parameter:
Besself
Butterworthf
Chebyshevf
Ellipticf
Inverse Chebyshevf
RCf - an “RC” conventional filter that most control systems use.

Functions ending in “p” allow entering the cut-off period as the main parameter:
Besselp
Butterworthp
Chebyshevp
Ellipticp
Inverse Chebyshevp
RCp - an “RC” conventional filter that most control systems use.

These are additional "RC" conventional filters that most control systems use:
Rct - where the time constant is entered.
Rck - where the “K” weighting factor is entered.

Functions ending in “zpsf” are Zero Phase Shift filters that allow entering the cut-off frequency as the main parameter. These are very useful where it is important to avoid position shift or phase lag. Therefore, they are usually used for CD Controls analysis.
Besselzpsf
Butterworthzpsf
Chebyshevzpsf
Ellipticzpsf
Inverse Chebyshevzpsf
RCzpsf

Functions ending in “zpsp” are Zero Phase Shift filters that allow entering the cut-off period as the main parameter. These are very useful where it is important to avoid position shift or phase lag. Therefore, they are usually used for CD Controls analysis.
Besselzpsp
Butterworthzpsp
Chebyshevzpsp
Ellipticzpsp
Inverse Chebyshevzpsp
RCzpsp

Functions ending in “zpst” or “zpsk” are Zero Phase Shift filters that allow entering the time constant or the “K” weighting factor as the main parameter. These are very useful where it is important to avoid position shift or phase lag. Therefore, they are usually used for CD Controls analysis.
RCzpst - an “RC” filter where the time constant is entered.
RCzpsk - an “RC” filter where the “K” weighting factor is entered.

Frequency Domain Functions

Brick Wall - A Brick Wall filter converts the data to the frequency domain, zeroes the amplitude of the specified region (depends whether it is set as a low pass, high pass, band pass or band reject filter) and then converts it back to the time domain. If you look at a Fourier plot, you will see an abrupt change in amplitude to zero in the affected region. There is a brickwallf function where the frequency is entered and a brickwallp function where the period is entered.
Edit Fourier - allows direct manipulation of the frequency spectrum. You can copy, interchange (swap), set or ramp any region of the frequency spectrum. The function converts the data to the frequency domain, performs the desired operation, and then converts it back to the time domain. There is a fourierf function where the frequency is entered and a fourierp function where the period is entered.

Array Functions

Force Mean (used for CD Controls analysis)
Insert
Replace
Reverse
Rotate
Fractional Rotate (used for CD Controls analysis.)
Symmetric (used for CD Controls analysis.)
Truncate

Calculus Functions

Derivative
Integral
Stress - used to calculate the second derivative - useful for CD Controls that have Slice Screws.

Constants

e
Pi

Logarithmic & Exponential Functions

Exponential E^X
Logarithm Logx(Y)
Natural Log In(X)
Power X^Y

Miscellaneous Functions

Absolute Value
Floor
Pid Output
Remainder
Round
Saturated Steam Temperature - calculates the temperature of saturated steam for any pressure using the 2006 ASME steam tables.
Saturated Steam Pressure - calculates the pressure of saturated steam for any temperature using the 2006 ASME steam tables.
Signal Generation - creates waveforms such as sines, cosines, triangle, square, saw-tooth, ramp and uniform or Gaussian white noise.
Square Root
Universal Root

Signal Processing Functions

Clip
Condense - decreases the sample rate of any data. This can be done by interpolation or averaging. The change factor does not need to be an integer.
Convolution - can be used to create custom filters that use forward as well as backward data; also useful in CD controls analysis.
Cumulative Sum
Deconvolution
Difference
Maximum
Minimum
Moving Average - averages the current and N previous samples to perform a specific type of filtering. Most control systems have this function so it can be emulated here.
Moving Median - calculates the median of the current and N previous samples to perform a specific type of filtering. This is is essentially a median filter and can be very useful to extract good data from very noisy and challenging data.
Normalize - normalizes the data such that the minimum becomes 0 and the maximum becomes 1.
Over Sample - increases the sample rate of any data. The change factor does not need to be an integer.
Z-average - like Moving Average but the averaging window is centred on the current sample, not ending on the current sample. This avoids shifting the data.
Z-median - like Moving Median but the median window is centred on the current sample, not ending on the current sample. This avoids shifting the data.

Trigonometric Functions

Sine
Cosine
Tangent
Inverse Sine
Inverse Cosine
Inverse Tangent
Hyperbolic Sine
Hyperbolic Cosine
Hyperbolic Tangent
Inverse Hyperbolic Sine
Inverse Hyperbolic Cosine
Inverse Hyperbolic Tangent

Unfilter Functions

These functions reverse the effects of a digital filter. These can be very useful in situations where you were unable to collect unfiltered data from your control system and need to estimate the original raw data. There are 4 versions to allow entering the original cut-off frequency, cut-off period, time constant or K weighting factor used by the control system. Theoretically, you could approximate the measurement upstream of a mixing tank for simulation purposes if you knew the volume and flow rate and assuming perfect and consistent mixing (e.g. estimate the consistency trend upstream of a trend knowing the downstream consistency).
UnfilterRCf
UnfilterRCp
UnfilterRCt
UnfilterRCk