Euler method: Difference between revisions

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 =={{header|EasyLang}}==
+[https://easylang.online/show/#cod=jZDdasJAEIXv5ykOFoo/uIyRoCnNE3gnuZcYVw3EbFjHxvTpy6zWqrTQuz3zc3bOly2RImJaIMWYDc9oe6oL5HVedVIWyBgCQwC8lZOvkS0xQj9jjJEtBxiicS0iM5vMozn6CwwhAzLUyVmQIomp8a7Axuft6maaYw1zcS1c5TyYExUH92ExZ+iy6mAyThGrEHsW9L49elraOg/9JYc4rLUCoCprC/lJMGFGcDNkSO/Y+XJDOtWWG9mDzZTU+1h+Wkzp8VLWdXrBhUptW3H1qnCuKusdxB6aBzaavh+qAQ6Zu/D2VFmPjkP4o9hGoz9SKFz1Twq6/4YeXoNTqCuGMI0UHeur3ZeVknh/RtNdpWCU3gzC6lVj+By1uwd4zaJgAx9MGAnz770Y/FcrAidM9AU=  Run it]
-[https://easylang.online/show/#cod=ZY9NasMwEIX3OsUH3bQpEZOUUgz1FXoHR1YSgSoFZYzR7YsUd5XN8L7HvPk5L8lxRlH/e8Ma4IUfv2pOuJxjSJfmKSPaRPG6lMRerHyx47XH9hzlzVhzK9nhl+gLVZg4ccfliH0Mdjnm0mqDGJJfw6xXxH78r5iaqIxUaWq9huhRvjk13FIodUPlfeS+Qe3Arr/TO6yxZi7TeilhNo+7DiJIrwdhEHmyP5Hh2T0iMhjzBw==  Run it]
 <syntaxhighlight>
+TR = 20
-func f t temp .
+K = -0.07
-   # Newton cooling
-   t = t
+func analytic T0 t .
-   return -0.07 * (temp - 20)
+   return TR + (T0 - TR) * pow 2.71828 (K * t)
 .
+ytxt = 95
-proc euler y0 a b s col . .
+proc draw_analytic a b . .
+   color 009
+   move 80 ytxt
+   ytxt -= 5
+   text "analytic"
+   for t = a to b
+      line t analytic 100 t
+   .
+.
+drawgrid
+linewidth 0.3
+textsize 3
+draw_analytic 0 100
+#
+func newton_cooling temp .
+   return K * (temp - TR)
+.
+proc draw_euler y0 a b step col . .
    color col
+   move 80 ytxt
-   linewidth 0.3
+   ytxt -= 5
+   text "step: " & step
    t = a
    y = y0
    while t < b
       line t y
-      t += s
+      t += step
-      y += s * f t y
+      y += step * newton_cooling y
    .
 .
+draw_euler 100 0 100 10 900
-drawgrid
-euler 100 0 100 10 900
+draw_euler 100 0 100 5 000
-euler 100 0 100 5 090
+draw_euler 100 0 100 2 090
-euler 100 0 100 2 009
 </syntaxhighlight>