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POHow to sum a function over a specific range in R?
 

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  1. POHow to sum a function over a specific range in R?
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    <p>Here are three columns:</p> <pre><code>indx vehID LocalY 1 2 35.381 2 2 39.381 3 2 43.381 4 2 47.38 5 2 51.381 6 2 55.381 7 2 59.381 8 2 63.379 9 2 67.383 10 2 71.398 11 2 75.401 12 2 79.349 13 2 83.233 14 2 87.043 15 2 90.829 16 2 94.683 17 2 98.611 18 2 102.56 19 2 106.385 20 2 110.079 21 2 113.628 22 2 117.118 23 2 120.6 24 2 124.096 25 2 127.597 26 2 131.099 27 2 134.595 28 2 138.081 29 2 141.578 30 2 145.131 31 2 148.784 32 2 152.559 33 2 156.449 34 2 160.379 35 2 164.277 36 2 168.15 37 2 172.044 38 2 176 39 2 179.959 40 2 183.862 41 2 187.716 42 2 191.561 43 2 195.455 44 2 199.414 45 2 203.417 46 2 207.43 47 2 211.431 48 2 215.428 49 2 219.427 50 2 223.462 51 2 227.422 52 2 231.231 53 2 235.001 54 2 238.909 55 2 242.958 56 2 247.137 57 2 251.247 58 2 255.292 59 2 259.31 60 2 263.372 61 2 267.54 62 2 271.842 63 2 276.256 64 2 280.724 65 2 285.172 </code></pre> <p>I want to create a new column called 'Smoothed Y' by applying the following formula: <img src="https://i.stack.imgur.com/AZOYv.jpg" alt="enter image description here"></p> <p>D=15, delta (triangular symbol) = 5, i = indx, x_alpha(tk) = LocalY, x_alpha(ti) = smoothed value</p> <p>I have tried using following code for first calculating Z: (Kernel below means the exp function)</p> <pre><code>t &lt;- 0.5 dt &lt;- 0.1 delta &lt;- t/dt d &lt;- 3*delta indx &lt;- a$indx for (i in indx) { initial &lt;- i-d end &lt;- i+d k &lt;- c(initial:end) for (n in k) { kernel &lt;- exp(-abs(i-n)/delta) z &lt;- sum(kernel) } } a$z &lt;- z print (a) </code></pre> <p>NOTE: 'a' is the imported data frame containing the three columns above.</p> <p>Although the values of computed function are fine but it doesn't sum up the values in variable z. How can I do summation over the range i-d to i+d for every indx value i?</p>
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    1. USumair durrani
    1. USumair durrani
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    1. COYou are overwriting "z" and "kernel" inside the "n" loop. Try `z = z + kernel`.
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      1. USFrank
    2. COCould you write a function that returned a value for Z(i,D) and another function that used it to return local sum_i. Then calculate that sum over the range of "i" where you would have sufficient data to form a sum.
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    3. CO`z=z+kernel` might work if you really want to loop. But, given the structure of the problem, it makes more sense to make the two vectors DWin mentioned. Your ending value is just the `Z'X/sum(Z)`
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