MagicPlot Manual

Plotting and nonlinear fitting software

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Help topics on the Next MagicPlot Release

These topics will be added in MagicPlot Help when next version will be released.

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Guess Peaks (Pro only)

MagicPlot can approximately locate peaks in spectrum. To locate peaks click on Guess button in Fit Curves tab of Fit Plot.

Guess peaks dialog

Using Spline for Baseline Subtraction

You can use cubic spline to fit and subtract baseline on Fit Plot. To create spline curve click on Add button in Fit Curves tab of Fit Plot. Created spline has 3 anchor points by default. Anchor points can be moved with mouse. Double click on spline curve to add new anchor point and double click on anchor point to remove it.

Tip: Don't use splines to subtract baselines which can be good fitted by line curve (line or constant baseline). You can subtract wide peaks by mistake using spline.

Using spline for baseline fitting

Fitting with Spline

Spline anchor point (x, y) coordinates are treated as fit parameters so you can perform fitting by spline. Note that the anchor point coordinates will be varied but the number of point will remain. You also can lock some parameters (usually x coordinates) by setting Lock check boxes in parameters table.

We recommend you to set appropriate fit intervals which contains only baseline without peaks. In such case Fit One Curve button is more usable than Fit by Sum button because the individual interval for current curve will be used and the interval from Fit Interval tab (which is used to fit by sum of curves) is ignored. Select spline curve and check Set Interval check box in the bottom of the panel to edit spline interval, then click on Fit One Curve button.

Set Baseline check box in spline row in curves table to subtract spline from data.

Setting Fit Interval for spline curve Spline subtraction result

Integrals and Statistics on Intervals

Setting intervals in Fit interval tab of Fit Plot is initially intended for setting data range which is used for fitting by sum of fit curves. However this tab can also be used to calculate integrals and statistics on these intervals (Statistics is only available in Pro edition). Data-Baseline is used to calculate the results.

MagicPlot is capable to integrate data on selected intervals and to calculate peak moments (x mean, variance, skewness, kurtosis). Spectrum line is treated as probability distribution curve: x values are treated as 'independent variable' and y values are treated as 'probability'. Standard statistical formulas are used to calculate moments.

Statistical data and integrals are automatically updated if x or y data is changed or intervals are changed.

Integration on intervals

All statistical data is summarized in the intervals table:

Statistics on intervals

Managing Intervals

Move interval borders with mouse. Double click on interval to split it at desired position. Right click opens context menu from which new intervals can be created on free space and existing intervals can be deleted or split.

Relative Integrals Calculation

MagicPlot is capable of calculation relative integrals to compare the relative intensity of spectrum lines. To compute relative integrals set Relative integrals check box. MagicPlot designate the smallest integral as 1 but you can enter a custom value. If you want not the smallest integral to be the reference point enter 1 firstly and than enter the value of desired integral relative to 1 to this field so that other integrals will be calculated relative to this new value.

Formulas

Property Formula
Integral Calculated using
Trapezoidal rule
X Mean (expected value) mu = nu_1
Variance sigma^2 = mu_2
Standard deviation sigma = sqrt{mu_2}
Skewness gamma_1 = {mu_3} / {sigma^3}
Kurtosis gamma_2 = {mu_4} / {sigma^4} − 3
Y Sum s = sum{k}{}{y_k}

Intermediate values are calculated as follows:

Property Formula
Raw moments nu_n = 1/s sum{k}{}{y_k {x_k}^n},~ n = 1…4
Normalization coefficient s = sum{k}{}{y_k}
Central moments mu_2 = nu_2 − {nu_1}^2
mu_3 = nu_3 − 3 nu_1 nu_2 + 2 {nu_1}^3
mu_4 = nu_4 − 4 nu_1 nu_2 + 6 {nu_1}^3 nu_2 − 3 {nu_1}^4

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Displaying Column Formulas in Table

MagicPlot indicates columns for which formulas or other evaluators (FFT, integral, etc.) are set with blue header color. You can see the formula in column header tool tip.

Table highlighting

On the screenshot above:

  • Column A has no formula
  • Column B has formula, auto recalculation is off
  • Column C has formula, auto recalculation is on, so this column is not editable

Fit Column Widths

To fit the width of one column double click on right separator line in table header. To fit selected columns widths double click one of column separators in table header.

Transform X or Y Column (Pro only)

You can quick transform X or Y data on Fit Plot by using Transform X/Y items in Processing menu. This menu items open set column formula dialog for table column which is used as X or Y. Note that this transformation affects the table with plot data.

Make Waterfall menu item opens waterfall window in which you can specify shift increment. MagicPlot tries to guess beautiful shift values on basis of the number of curves and current scale.

Waterfall window

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MagicPlot can be minimized to task bar while Calculator window can be still on top

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new.1287642513.txt.gz · Last modified: Sun Nov 8 12:20:32 2015 (external edit)