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14 .. Prerequisites |
14 .. Prerequisites |
15 .. ------------- |
15 .. ------------- |
16 |
16 |
17 .. 1. getting started with arrays |
17 .. 1. getting started with arrays |
18 |
18 |
19 |
19 .. #[anand: internal reviewer not mentioned] |
20 .. Author : Puneeth |
20 .. Author : Puneeth |
21 Internal Reviewer : |
21 Internal Reviewer : |
22 External Reviewer : |
22 External Reviewer : |
23 Checklist OK? : <put date stamp here, if OK> [2010-10-05] |
23 Language Reviewer : Bhanukiran |
|
24 Checklist OK? : <06-11-2010, Anand, OK> [2010-10-05] |
24 |
25 |
25 Script |
26 Script |
26 ------ |
27 ------ |
27 |
28 |
28 {{{ Screen shows welcome slide }}} |
29 {{{ Screen shows welcome slide }}} |
124 |
125 |
125 :: |
126 :: |
126 |
127 |
127 C[-1] = 0 |
128 C[-1] = 0 |
128 |
129 |
129 Now, how do we access one column of C? As with accessing |
130 Now, how do we access one column of C? As with accessing individual |
130 individual elements, the column is the second parameter to be |
131 elements, the column is the second parameter to be specified (after |
131 specified (after the comma). The first parameter, is now replaced |
132 the comma). The first parameter, is replaced with a ``:``. This |
132 with a ``:`` to say, that we want all the elements of that |
133 specifies that we want all the elements of that dimension, instead of |
133 dimension, instead of one particular element. We access the third |
134 just one particular element. We access the third column by |
134 column by |
|
135 |
135 |
136 :: |
136 :: |
137 |
137 |
138 C[:, 2] |
138 C[:, 2] |
139 |
139 |
228 |
228 |
229 C[0:3, 2] |
229 C[0:3, 2] |
230 |
230 |
231 to get the elements of rows indexed from 0 to 3, 3 not included |
231 to get the elements of rows indexed from 0 to 3, 3 not included |
232 and column indexed 2. Note that, the index before the colon is |
232 and column indexed 2. Note that, the index before the colon is |
233 included and the index after it is not included, in the slice that |
233 included and the index after it is not included in the slice that |
234 we have obtained. This is very similar to the ``range`` function, |
234 we have obtained. This is very similar to the ``range`` function, |
235 where ``range`` returns a list, in which the upper limit or stop |
235 where ``range`` returns a list, in which the upper limit or stop |
236 value is not included. |
236 value is not included. |
237 |
237 |
238 Now, if we wish to access the elements of row with index 2, and in |
238 Now, if we wish to access the elements of row with index 2, and in |
267 |
267 |
268 C[1:5, 0] |
268 C[1:5, 0] |
269 |
269 |
270 gives the elements [21, 31, 41, 0] |
270 gives the elements [21, 31, 41, 0] |
271 |
271 |
272 Note that when specifying ranges, if you are starting from or |
272 Note that when specifying ranges, if you are starting from the |
273 going up-to the end, the corresponding element may be dropped. So, |
273 beginning or going up-to the end, the corresponding element may be |
274 in the previous example to obtain [11, 21, 31, 41], we could have |
274 dropped. So, in the previous example to obtain [11, 21, 31, 41], we |
275 simply said, |
275 could have simply said, :: |
276 :: |
|
277 |
276 |
278 C[:4, 0] |
277 C[:4, 0] |
279 |
278 |
280 and |
279 and |
281 :: |
280 :: |
321 |
320 |
322 {{ show slide containing Question 5 }} |
321 {{ show slide containing Question 5 }} |
323 |
322 |
324 %%5%% Obtain the square in the center of the image. |
323 %%5%% Obtain the square in the center of the image. |
325 |
324 |
326 Following is an exercise that you must do. |
325 Please, pause the video here. Do the exercises and then continue. |
327 |
326 |
328 {{ show slide containing Solution 5 }} |
327 {{ show slide containing Solution 5 }} |
329 |
328 |
330 :: |
329 :: |
331 |
330 |
381 |
380 |
382 C[::4, 1:4] |
381 C[::4, 1:4] |
383 |
382 |
384 gives the elements [[12, 13, 14], [0, 0, 0]] |
383 gives the elements [[12, 13, 14], [0, 0, 0]] |
385 |
384 |
386 Now, that we know how to stride over an image, we can drop |
385 Now, that we know how to stride over an array, we can drop |
387 alternate rows and columns out of the image in I. |
386 alternate rows and columns out of the image in I. |
388 :: |
387 :: |
389 |
388 |
390 I[::2, ::2] |
389 I[::2, ::2] |
391 |
390 |
421 .. |
420 .. |
422 Local Variables: |
421 Local Variables: |
423 mode: rst |
422 mode: rst |
424 indent-tabs-mode: nil |
423 indent-tabs-mode: nil |
425 sentence-end-double-space: nil |
424 sentence-end-double-space: nil |
426 fill-column: 75 |
425 fill-column: 70 |
427 End: |
426 End: |