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| 1 | +{{alias}}( A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN ) |
| 2 | + Computes the real Schur factorization of a 2-by-2 real nonsymmetric |
| 3 | + matrix using an orthogonal similarity transformation. |
| 4 | + |
| 5 | + Given matrix: |
| 6 | + |
| 7 | + [ A B ] |
| 8 | + [ C D ] |
| 9 | + |
| 10 | + The routine computes an orthogonal rotation (cosine CS, sine SN) such |
| 11 | + that: |
| 12 | + |
| 13 | + Q^T * [ A B ] * Q = [ AA BB ] |
| 14 | + [ C D ] [ CC DD ] |
| 15 | + |
| 16 | + where Q is a 2x2 rotation matrix: |
| 17 | + |
| 18 | + Q = [ CS SN ] |
| 19 | + [ -SN CS ] |
| 20 | + |
| 21 | + and the result is either real upper triangular (real eigenvalues) or |
| 22 | + 2x2 block diagonal (complex conjugate eigenvalues). |
| 23 | + |
| 24 | + Indexing is relative to the first index. To introduce an offset, use |
| 25 | + typed array views. |
| 26 | + |
| 27 | + Parameters |
| 28 | + ---------- |
| 29 | + A: Float64Array |
| 30 | + Input element A(1,1). |
| 31 | + |
| 32 | + B: Float64Array |
| 33 | + Input element A(1,2). |
| 34 | + |
| 35 | + C: Float64Array |
| 36 | + Input element A(2,1). |
| 37 | + |
| 38 | + D: Float64Array |
| 39 | + Input element A(2,2). |
| 40 | + |
| 41 | + RT1R: Float64Array |
| 42 | + Output: real part of the first eigenvalue. |
| 43 | + |
| 44 | + RT1I: Float64Array |
| 45 | + Output: imaginary part of the first eigenvalue. |
| 46 | + |
| 47 | + RT2R: Float64Array |
| 48 | + Output: real part of the second eigenvalue. |
| 49 | + |
| 50 | + RT2I: Float64Array |
| 51 | + Output: imaginary part of the second eigenvalue. |
| 52 | + |
| 53 | + CS: Float64Array |
| 54 | + Output: cosine of the rotation. |
| 55 | + |
| 56 | + SN: Float64Array |
| 57 | + Output: sine of the rotation. |
| 58 | + |
| 59 | + Returns |
| 60 | + ------- |
| 61 | + undefined |
| 62 | + |
| 63 | + Examples |
| 64 | + -------- |
| 65 | + > var Float64Array = require( '@stdlib/array/float64' ); |
| 66 | + > var dlanv2 = require( '@stdlib/lapack/base/dlanv2' ); |
| 67 | + |
| 68 | + > var A = new Float64Array( [ 4.0 ] ); |
| 69 | + > var B = new Float64Array( [ -5.0 ] ); |
| 70 | + > var C = new Float64Array( [ 2.0 ] ); |
| 71 | + > var D = new Float64Array( [ -3.0 ] ); |
| 72 | + > var RT1R = new Float64Array( 1 ); |
| 73 | + > var RT1I = new Float64Array( 1 ); |
| 74 | + > var RT2R = new Float64Array( 1 ); |
| 75 | + > var RT2I = new Float64Array( 1 ); |
| 76 | + > var CS = new Float64Array( 1 ); |
| 77 | + > var SN = new Float64Array( 1 ); |
| 78 | + |
| 79 | + > dlanv2( A, B, C, D, RT1R, RT1I, RT2R, RT2I, CS, SN ); |
| 80 | + |
| 81 | + > A |
| 82 | + <Float64Array>[ 2.0 ] |
| 83 | + > B |
| 84 | + <Float64Array>[ -7.0 ] |
| 85 | + > C |
| 86 | + <Float64Array>[ 0.0 ] |
| 87 | + > D |
| 88 | + <Float64Array>[ -1.0 ] |
| 89 | + > RT1R |
| 90 | + <Float64Array>[ 2.0 ] |
| 91 | + > RT1I |
| 92 | + <Float64Array>[ 0.0 ] |
| 93 | + > RT2R |
| 94 | + <Float64Array>[ -1.0 ] |
| 95 | + > RT2I |
| 96 | + <Float64Array>[ 0.0 ] |
| 97 | + > CS |
| 98 | + <Float64Array>[ ~0.93 ] |
| 99 | + > SN |
| 100 | + <Float64Array>[ ~0.34 ] |
| 101 | + |
| 102 | +{{alias}}.ndarray( A,oa,B,ob,C,oc,D,od,R1,or1,I1,oi1,R2,or2,I2,oi2,CS,ocs,SN,osn ) |
| 103 | + |
| 104 | + Computes the Schur factorization of a 2-by-2 real nonsymmetric matrix |
| 105 | + using alternative indexing semantics. |
| 106 | + |
| 107 | + Given matrix: |
| 108 | + |
| 109 | + [ A B ] |
| 110 | + [ C D ] |
| 111 | + |
| 112 | + The routine computes an orthogonal rotation (cosine CS, sine SN) such |
| 113 | + that: |
| 114 | + |
| 115 | + Q^T * [ A B ] * Q = [ AA BB ] |
| 116 | + [ C D ] [ CC DD ] |
| 117 | + |
| 118 | + where Q is a 2x2 rotation matrix: |
| 119 | + |
| 120 | + Q = [ CS SN ] |
| 121 | + [ -SN CS ] |
| 122 | + |
| 123 | + and the result is either real upper triangular (real eigenvalues) or |
| 124 | + 2x2 block diagonal (complex conjugate eigenvalues). |
| 125 | + |
| 126 | + While typed array views mandate a view offset based on the underlying |
| 127 | + buffer, the offset parameters support indexing semantics based on starting |
| 128 | + indices. |
| 129 | + |
| 130 | + Parameters |
| 131 | + ---------- |
| 132 | + A: Float64Array |
| 133 | + Input element A(1,1). |
| 134 | + |
| 135 | + oa: integer |
| 136 | + Starting index for `A`. |
| 137 | + |
| 138 | + B: Float64Array |
| 139 | + Input element A(1,2). |
| 140 | + |
| 141 | + ob: integer |
| 142 | + Starting index for `B`. |
| 143 | + |
| 144 | + C: Float64Array |
| 145 | + Input element A(2,1). |
| 146 | + |
| 147 | + oc: integer |
| 148 | + Starting index for `C`. |
| 149 | + |
| 150 | + D: Float64Array |
| 151 | + Input element A(2,2). |
| 152 | + |
| 153 | + od: integer |
| 154 | + Starting index for `D`. |
| 155 | + |
| 156 | + R1: Float64Array |
| 157 | + Output: real part of the first eigenvalue. |
| 158 | + |
| 159 | + or1: integer |
| 160 | + Starting index for `R1`. |
| 161 | + |
| 162 | + I1: Float64Array |
| 163 | + Output: imaginary part of the first eigenvalue. |
| 164 | + |
| 165 | + oi1: integer |
| 166 | + Starting index for `I1`. |
| 167 | + |
| 168 | + R2: Float64Array |
| 169 | + Output: real part of the second eigenvalue. |
| 170 | + |
| 171 | + or2: integer |
| 172 | + Starting index for `R2`. |
| 173 | + |
| 174 | + I2: Float64Array |
| 175 | + Output: imaginary part of the second eigenvalue. |
| 176 | + |
| 177 | + oi2: integer |
| 178 | + Starting index for `I2`. |
| 179 | + |
| 180 | + CS: Float64Array |
| 181 | + Output: cosine of the rotation. |
| 182 | + |
| 183 | + ocs: integer |
| 184 | + Starting index for `CS`. |
| 185 | + |
| 186 | + SN: Float64Array |
| 187 | + Output: sine of the rotation. |
| 188 | + |
| 189 | + osn: integer |
| 190 | + Starting index for `SN`. |
| 191 | + |
| 192 | + Examples |
| 193 | + -------- |
| 194 | + > var Float64Array = require( '@stdlib/array/float64' ); |
| 195 | + > var A = new Float64Array( [ 0.0, 4.0 ] ); |
| 196 | + > var B = new Float64Array( [ 0.0, -5.0 ] ); |
| 197 | + > var C = new Float64Array( [ 0.0, 2.0 ] ); |
| 198 | + > var D = new Float64Array( [ 0.0, -3.0 ] ); |
| 199 | + > var RT1R = new Float64Array( 2 ); |
| 200 | + > var RT1I = new Float64Array( 2 ); |
| 201 | + > var RT2R = new Float64Array( 2 ); |
| 202 | + > var RT2I = new Float64Array( 2 ); |
| 203 | + > var CS = new Float64Array( 2 ); |
| 204 | + > var SN = new Float64Array( 2 ); |
| 205 | + |
| 206 | + > dlanv2.ndarray( A, 1, B, 1, C, 1, D, 1, |
| 207 | + RT1R, 1, RT1I, 1, RT2R, 1, RT2I, 1, CS, 1, SN, 1 ); |
| 208 | + |
| 209 | + > A |
| 210 | + <Float64Array>[ 0.0, 2.0 ] |
| 211 | + > C |
| 212 | + <Float64Array>[ 0.0, 0.0 ] |
| 213 | + > RT1R |
| 214 | + <Float64Array>[ 0.0, 2.0 ] |
| 215 | + > RT2R |
| 216 | + <Float64Array>[ 0.0, -1.0 ] |
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