Spatial Data Science with R - Day1

Library

library(raster)

RasterLayer with the default parameters

x <- raster()
x

class      : RasterLayer 
dimensions : 180, 360, 64800  (nrow, ncol, ncell)
resolution : 1, 1  (x, y)
extent     : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
crs        : +proj=longlat +datum=WGS84 +no_defs 

With other parameters

x <- raster(ncol=36, 
            nrow=18, 
            xmn=-1000, 
            xmx=1000, 
            ymn=-100, 
            ymx=900)
x

class      : RasterLayer 
dimensions : 18, 36, 648  (nrow, ncol, ncell)
resolution : 55.55556, 55.55556  (x, y)
extent     : -1000, 1000, -100, 900  (xmin, xmax, ymin, ymax)
crs        : NA 

hasValues(x)

[1] FALSE

use the ‘values’ function

values(x) <- 1:ncell(x)
hasValues(x)

[1] TRUE

Values

values(x)[1:648]

  [1]   1   2   3   4   5   6
  [7]   7   8   9  10  11  12
 [13]  13  14  15  16  17  18
 [19]  19  20  21  22  23  24
 [25]  25  26  27  28  29  30
 [31]  31  32  33  34  35  36
 [37]  37  38  39  40  41  42
 [43]  43  44  45  46  47  48
 [49]  49  50  51  52  53  54
 [55]  55  56  57  58  59  60
 [61]  61  62  63  64  65  66
 [67]  67  68  69  70  71  72
 [73]  73  74  75  76  77  78
 [79]  79  80  81  82  83  84
 [85]  85  86  87  88  89  90
 [91]  91  92  93  94  95  96
 [97]  97  98  99 100 101 102
[103] 103 104 105 106 107 108
[109] 109 110 111 112 113 114
[115] 115 116 117 118 119 120
[121] 121 122 123 124 125 126
[127] 127 128 129 130 131 132
[133] 133 134 135 136 137 138
[139] 139 140 141 142 143 144
[145] 145 146 147 148 149 150
[151] 151 152 153 154 155 156
[157] 157 158 159 160 161 162
[163] 163 164 165 166 167 168
[169] 169 170 171 172 173 174
[175] 175 176 177 178 179 180
[181] 181 182 183 184 185 186
[187] 187 188 189 190 191 192
[193] 193 194 195 196 197 198
[199] 199 200 201 202 203 204
[205] 205 206 207 208 209 210
[211] 211 212 213 214 215 216
[217] 217 218 219 220 221 222
[223] 223 224 225 226 227 228
[229] 229 230 231 232 233 234
[235] 235 236 237 238 239 240
[241] 241 242 243 244 245 246
[247] 247 248 249 250 251 252
[253] 253 254 255 256 257 258
[259] 259 260 261 262 263 264
[265] 265 266 267 268 269 270
[271] 271 272 273 274 275 276
[277] 277 278 279 280 281 282
[283] 283 284 285 286 287 288
[289] 289 290 291 292 293 294
[295] 295 296 297 298 299 300
[301] 301 302 303 304 305 306
[307] 307 308 309 310 311 312
[313] 313 314 315 316 317 318
[319] 319 320 321 322 323 324
[325] 325 326 327 328 329 330
[331] 331 332 333 334 335 336
[337] 337 338 339 340 341 342
[343] 343 344 345 346 347 348
[349] 349 350 351 352 353 354
[355] 355 356 357 358 359 360
[361] 361 362 363 364 365 366
[367] 367 368 369 370 371 372
[373] 373 374 375 376 377 378
[379] 379 380 381 382 383 384
[385] 385 386 387 388 389 390
[391] 391 392 393 394 395 396
[397] 397 398 399 400 401 402
[403] 403 404 405 406 407 408
[409] 409 410 411 412 413 414
[415] 415 416 417 418 419 420
[421] 421 422 423 424 425 426
[427] 427 428 429 430 431 432
[433] 433 434 435 436 437 438
[439] 439 440 441 442 443 444
[445] 445 446 447 448 449 450
[451] 451 452 453 454 455 456
[457] 457 458 459 460 461 462
[463] 463 464 465 466 467 468
[469] 469 470 471 472 473 474
[475] 475 476 477 478 479 480
[481] 481 482 483 484 485 486
[487] 487 488 489 490 491 492
[493] 493 494 495 496 497 498
[499] 499 500 501 502 503 504
[505] 505 506 507 508 509 510
[511] 511 512 513 514 515 516
[517] 517 518 519 520 521 522
[523] 523 524 525 526 527 528
[529] 529 530 531 532 533 534
[535] 535 536 537 538 539 540
[541] 541 542 543 544 545 546
[547] 547 548 549 550 551 552
[553] 553 554 555 556 557 558
[559] 559 560 561 562 563 564
[565] 565 566 567 568 569 570
[571] 571 572 573 574 575 576
[577] 577 578 579 580 581 582
[583] 583 584 585 586 587 588
[589] 589 590 591 592 593 594
[595] 595 596 597 598 599 600
[601] 601 602 603 604 605 606
[607] 607 608 609 610 611 612
[613] 613 614 615 616 617 618
[619] 619 620 621 622 623 624
[625] 625 626 627 628 629 630
[631] 631 632 633 634 635 636
[637] 637 638 639 640 641 642
[643] 643 644 645 646 647 648

Plot

plot(x)

File

filename <- system.file("external/test.grd", package="raster")
filename

[1] "C:/Users/154455/AppData/Local/R/win-library/4.3/raster/external/test.grd"

r <- raster(filename)

Plot

plot(r, main='RasterLayer from file')

create three identical RasterLayer objects

r1 <- r2 <- r3 <- raster(nrow=10, ncol=10)

Assign random cell values

values(r1) <- runif(ncell(r1))
values(r2) <- runif(ncell(r2))
values(r3) <- runif(ncell(r3))

combine three RasterLayer objects into a RasterStack

s <- stack(r1, r2, r3)
s

class      : RasterStack 
dimensions : 10, 10, 100, 3  (nrow, ncol, ncell, nlayers)
resolution : 36, 18  (x, y)
extent     : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
crs        : +proj=longlat +datum=WGS84 +no_defs 
names      :     layer.1,     layer.2,     layer.3 
min values : 0.033881011, 0.019854612, 0.002501915 
max values :   0.9875726,   0.9941112,   0.9956419 

nlayers(s)

[1] 3

combine three RasterLayer objects into a RasterBrick

b1 <- brick(r1, r2, r3)

equivalent to:

b2 <- brick(s)

create a RasterBrick from file

filename <- system.file("external/rlogo.grd", package="raster")
filename

[1] "C:/Users/154455/AppData/Local/R/win-library/4.3/raster/external/rlogo.grd"

r <- raster(filename)

Plot

plot(r, main='RasterLayer from file')

Raster brick

b <- brick(filename)
b

class      : RasterBrick 
dimensions : 77, 101, 7777, 3  (nrow, ncol, ncell, nlayers)
resolution : 1, 1  (x, y)
extent     : 0, 101, 0, 77  (xmin, xmax, ymin, ymax)
crs        : +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
source     : rlogo.grd 
names      : red, green, blue 
min values :   0,     0,    0 
max values : 255,   255,  255 

nlayers(b)

[1] 3

extract a single RasterLayer

r <- raster(b, layer=2)
r

class      : RasterLayer 
band       : 2  (of  3  bands)
dimensions : 77, 101, 7777  (nrow, ncol, ncell)
resolution : 1, 1  (x, y)
extent     : 0, 101, 0, 77  (xmin, xmax, ymin, ymax)
crs        : +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
source     : rlogo.grd 
names      : green 
values     : 0, 255  (min, max)

equivalent to creating it from disk

r <- raster(filename, band=2)
r

class      : RasterLayer 
band       : 2  (of  3  bands)
dimensions : 77, 101, 7777  (nrow, ncol, ncell)
resolution : 1, 1  (x, y)
extent     : 0, 101, 0, 77  (xmin, xmax, ymin, ymax)
crs        : +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs 
source     : rlogo.grd 
names      : green 
values     : 0, 255  (min, max)

Reference - https://rspatial.org/raster/index.html