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# streamtube

Create 3-D stream tube plot

## Syntax

streamtube(X,Y,Z,U,V,W,startx,starty,startz)
streamtube(U,V,W,startx,starty,startz)
streamtube(vertices,X,Y,Z,divergence)
streamtube(vertices,divergence)
streamtube(vertices,width)
streamtube(vertices)
streamtube(...,[scale n])
streamtube(axes_handle,...)
h = streamtube(...z)

## Description

streamtube(X,Y,Z,U,V,W,startx,starty,startz) draws stream tubes from vector volume data U, V, W.

The arrays X, Y, and Z, which define the coordinates for U, V, and W, must be monotonic, but do not need to be uniformly spaced. X, Y, and Z must have the same number of elements, as if produced by meshgrid.

startx, starty, and startz define the starting positions of the streamlines at the center of the tubes. The section Specifying Starting Points for Stream Plots provides more information on defining starting points.

The width of the tubes is proportional to the normalized divergence of the vector field.

streamtube(U,V,W,startx,starty,startz) assumes X, Y, and Z are determined by the expression

```[X,Y,Z] = meshgrid(1:n,1:m,1:p)
```

where [m,n,p] = size(U).

streamtube(vertices,X,Y,Z,divergence) assumes precomputed streamline vertices and divergence. vertices is a cell array of streamline vertices (as produced by stream3). X, Y, Z, and divergence are 3-D arrays.

streamtube(vertices,divergence) assumes X, Y, and Z are determined by the expression

```[X,Y,Z] = meshgrid(1:n,1:m,1:p)
```

where [m,n,p] = size(divergence).

streamtube(vertices,width) specifies the width of the tubes in the cell array of vectors, width. The size of each corresponding element of vertices and width must be equal. width can also be a scalar, specifying a single value for the width of all stream tubes.

streamtube(vertices) selects the width automatically.

streamtube(...,[scale n]) scales the width of the tubes by scale. The default is scale = 1. When the stream tubes are created, using start points or divergence, specifying scale = 0 suppresses automatic scaling. n is the number of points along the circumference of the tube. The default is n = 20.

streamtube(axes_handle,...) plots into the axes object with the handle axes_handle instead of into the current axes object (gca).

h = streamtube(...z) returns a vector of handles (one per start point) to surface objects used to draw the stream tubes.

## Examples

This example uses stream tubes to indicate the flow in the wind data set. Inputs include the coordinates, vector field components, and starting location for the stream tubes.

```figure
[sx sy sz] = meshgrid(80,20:10:50,0:5:15);
streamtube(x,y,z,u,v,w,sx,sy,sz);
% Define viewing and lighting
view(3)
axis tight
camlight; lighting gouraud
```

This example uses precalculated vertex data (stream3) and divergence (divergence).

```figure
[sx sy sz] = meshgrid(80,20:10:50,0:5:15);
verts = stream3(x,y,z,u,v,w,sx,sy,sz);
div = divergence(x,y,z,u,v,w);
streamtube(verts,x,y,z,-div);
% Define viewing and lighting
view(3)
axis tight