A Guide on Spectral Methods Applied to Discrete Data in One Dimension

<div>Oversampled signal <svg height="12.7178pt" id="M141" style="vertical-align:-3.42947pt" version="1.1" viewbox="-0.0498162 -9.28833 21.1342 12.7178" width="21.1342pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M556 393C556 426 537 448 514 448C496 448 478 435 471 420C468 414 462 401 466 394C473 382 480 368 480 346C480 268 392 143 338 67H336C329 163 319 253 309 330S286 448 254 448C215 448 160 383 127 337L143 311C167 344 200 373 208 373S222 365 229 320C246 214 264 66 268 -20C219 -83 131 -171 17 -239L25 -261L137 -235C248 -110 273 -79 335 8C384 77 481 215 520 287C544 332 556 363 556 393Z" id="g113-122"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="579" vert-adv-y="579" xpluscharwidth="7.527"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,7.529,0)"><path d="M300 -147C201 -63 143 98 143 270S200 602 300 686L282 710C136 610 70 450 70 271V270C70 89 136 -72 282 -170L300 -147Z" id="g113-41"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="346" vert-adv-y="346" xpluscharwidth="12.027000000000001"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,12.027,0)"><path d="M324 430H196L233 583L223 592L145 529L120 430H54L29 396L31 388H111L56 126C33 15 54 -12 77 -12C137 -12 214 57 250 95L233 119C208 92 155 59 138 59C126 59 120 70 131 125L186 390L298 394L324 430Z" id="g113-117"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="341" vert-adv-y="341" xpluscharwidth="16.46"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,16.46,0)"><path d="M275 270C275 450 212 609 64 710L45 686C145 604 203 442 203 270S147 -63 45 -147L64 -170C213 -68 275 89 275 270Z" id="g113-42"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="346" vert-adv-y="346" xpluscharwidth="20.958000000000002"></glyph.data></g></svg>. Band limitation is achieved by definition of the signal. Mention that the first sample and the <svg height="11.9087pt" id="M142" style="vertical-align:-3.2728pt" version="1.1" viewbox="-0.0498162 -8.6359 31.5471 11.9087" width="31.5471pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M244 607C244 633 228 655 200 655C166 655 146 618 146 594C146 564 166 546 191 546C221 546 244 574 244 607ZM222 91L209 114C184 94 148 66 133 66C127 66 124 73 130 96L201 370C213 416 211 448 191 448C162 448 88 407 29 352L42 328C73 354 104 371 114 371C120 371 119 365 115 345L53 92C32 5 45 -12 68 -12C103 -12 186 50 222 91Z" id="g113-106"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="273" vert-adv-y="273" xpluscharwidth="3.549"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,3.484,3.132)"><path d="M298 36L289 62C276 55 253 45 228 45C202 45 169 60 169 141V397H276C289 405 292 426 282 437H169V574L155 576L90 509V437H45L17 408L21 397H90V107C90 28 125 -12 188 -12C198 -12 213 -8 230 1L298 36Z" id="g190-117"></path><glyph.data ascent="989" descent="-360" horiz-adv-x="305" vert-adv-y="305" xpluscharwidth="6.259490850000001"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,6.314,3.132)"><path d="M513 0V26C455 31 447 37 447 103V278C447 398 390 449 309 449C255 449 202 412 166 376V712C127 700 67 684 19 677V653C85 647 87 643 87 580V103C87 37 79 31 19 26L18 0H231V26C171 32 166 39 166 103V341C194 373 232 392 270 392C337 392 368 351 368 269V103C368 38 360 32 302 26V0H513Z" id="g190-105"></path><glyph.data ascent="989" descent="-360" horiz-adv-x="534" vert-adv-y="534" xpluscharwidth="11.17338398"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,14.606,0)"><path d="M535 230V280H323V490H265V280H52V230H265V-3H323V230H535Z" id="g117-36"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="587" vert-adv-y="587" xpluscharwidth="22.237000000000002"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,25.142,0)"><path d="M384 0V27C293 34 287 42 287 114V635C232 613 172 594 109 583V559L157 557C201 555 205 550 205 499V114C205 42 199 34 109 27V0H384Z" id="g113-50"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="480" vert-adv-y="480" xpluscharwidth="31.381999999999998"></glyph.data></g></svg> sample at <svg height="8.55521pt" id="M143" style="vertical-align:-0.2063904pt" version="1.1" viewbox="-0.0498162 -8.34882 25.736 8.55521" width="25.736pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M324 430H196L233 583L223 592L145 529L120 430H54L29 396L31 388H111L56 126C33 15 54 -12 77 -12C137 -12 214 57 250 95L233 119C208 92 155 59 138 59C126 59 120 70 131 125L186 390L298 394L324 430Z" id="g113-117"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="341" vert-adv-y="341" xpluscharwidth="4.433"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,8.065,0)"><path d="M535 323V373H52V323H535ZM535 138V188H52V138H535Z" id="g117-34"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="587" vert-adv-y="587" xpluscharwidth="15.696"></glyph.data></g><g transform="matrix(.013,0,0,-0.013,19.328,0)"><path d="M384 0V27C293 34 287 42 287 114V635C232 613 172 594 109 583V559L157 557C201 555 205 550 205 499V114C205 42 199 34 109 27V0H384Z" id="g113-50"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="480" vert-adv-y="480" xpluscharwidth="25.567999999999998"></glyph.data></g></svg> would be the same, because of the periodicity of the signal.</div>

Journal of Applied Mathematics

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Figure 2

Figure 2: A Guide on Spectral Methods Applied to Discrete Data in One Dimension 