# surfht

Interactive contour plot

## Syntax

``surfht(z)``
``surfht(x,y,z)``

## Description

````surfht(z)` creates an interactive contour plot of the data in matrix `z`. `surfht` treats the values in `z` as the height above the plane.```

example

````surfht(x,y,z)` creates an interactive contour plot of the data in matrix `z`, using the x-axis values contained in `x` and the y-axis values contained in `y`.```

## Examples

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This example shows how to use `surfht` to create an interactive contour plot.

Create a grid of the (x,y) domain from (-2,-2) to (2,2) using `meshgrid`.

`[x,y] = meshgrid(-2:0.2:2,-2:0.2:2);`

Evaluate the function z(x,y) = x × exp(-x2y2) over this domain.

`z = x.*exp(-x.^2 - y.^2);`

Open an interactive contour plot. Since `meshgrid` creates a grid of the x and y values, open the plot using the first row of x and the first column of y.

`surfht(x(1,:),y(:,1),z)` The figure shows a contour plot of the z values along the specified x- and y-axes.

Click the plot to evaluate z at the (x,y) coordinates indicated by the intersecting white lines. For example, at x = 0.71041 and y = 0.025723, the value of z is 0.41827.

Alternatively, enter values in the fields labeled ```X Value``` and `Y Value` to evaluate z at the specified coordinates. For example, evaluate z at x = 0.5 and y = 1. The value of z is 0.1397.

## Input Arguments

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z-axis values for contour plot, specified as a numeric matrix.

`surfht` treats the values in `z` as the height above the plane. By default, the x-axis values of the plot are the column indices of `z`, and the y-axis values of the plot are the row indices of `z`. To change the x- and y-axis values, specify `x` and `y`, respectively.

Data Types: `single` | `double`

x-axis values for contour plot, specified as a numeric vector. The length of `x` must match the number of columns in `z`.

Data Types: `single` | `double`

y-axis values for contour plot, specified as a numeric vector. The length of `y` must match the number of rows in `z`.

Data Types: `single` | `double`

### Tips

• The intersection of the vertical and horizontal reference lines on the interactive plot defines the current x value and y value.

• Drag the dotted white reference lines to watch the interpolated z value (at the top of the plot) update simultaneously.

• Alternatively, obtain a specific interpolated z value by typing the x value and y value into editable text fields on the x-axis and y-axis, respectively.