Texas Instruments TI89 Developer Guide - Page 657
XCvtPtoF, CptFuncX, for the active graph window
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Appendix A: System Routines - Graphing 615 YCvtFtoP Declaration: SSHORT YCvtFtoP (BCD16 y, GR_WIN_VARS * ptr) Category: Graphing Description: Converts the input floating point y coordinate to a pixel row number based on the specified graph viewing window. Inputs: y - Floating point y coordinate. Valid y is not limited to the actual viewing window, allowing computation of off-screen pixels above (negative) or below the visible window. ptr - Pointer to the GR_WIN_VARS struct to use for viewing window values (gr_active for the active graph window, gr_other for the second graph in two graph mode). Outputs: Returns a pixel row number or GXY_INVALID if the value computed is outside the range of SSHORT. The topmost row in a window is row 0. Assumptions: Assumes an x, y coordinate system, even in 3D mode. Side Effects: None Availability: All versions of the TI-89 / TI-92 Plus. TI-89 / TI-92 Plus Differences: None See Also: XCvtPtoF, CptFuncX, YCvtPtoF, XCvtFtoP Example: /* convert float coordinates to pixel coordinates and plot point on the pixel */ col = XCvtFtoP( x, gr_active ); /* find pixel column */ row = YCvtFtoP( y, gr_active ); /* find pixel row */ WinPixSet( gr_active->grwinp, col, row ); /* plot point */ TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001
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