http://202.127.29.3/~shen/wiki/index.php?action=history&feed=atom&title=%E7%89%B9%E6%AE%8A%E5%80%BC_%21Values 2026-05-13T07:08:40Z 本wiki上该页面的版本历史 MediaWiki 1.38.1 http://202.127.29.3/~shen/wiki/index.php?title=%E7%89%B9%E6%AE%8A%E5%80%BC_!Values&diff=2662&oldid=prev 2017-06-05T13:55:48Z

<p>创建页面，内容为“:NAN and Infinity value IDL&gt; help,!Values,/str ** Structure !VALUES, 4 tags, length=24, data length=24: F_INFINITY FLOAT Inf F_NAN...”</p> <p><b>新页面</b></p><div>:NAN and Infinity value <br /> <br /> IDL&gt; help,!Values,/str<br /> ** Structure !VALUES, 4 tags, length=24, data length=24:<br /> F_INFINITY FLOAT Inf<br /> F_NAN FLOAT NaN<br /> D_INFINITY DOUBLE Infinity<br /> D_NAN DOUBLE NaN<br /> Inf还可取负<br /> IDL&gt; print,-1*!Values.F_INFINITY<br /> -Inf<br /> 问题：如何给一个整数变量赋一个NAN 或者 INFINITY<br /> <br /> :F_INFINITY可以和浮点数做比较 F_NAN不能<br /> B = [1.0, 2.0, !VALUES.F_NAN]<br /> IDL&gt; PRINT, WHERE(B EQ !VALUES.F_NAN<br /> -1<br /> :在求平均等计算时，设置/NAN开关，可将这些数忽略<br /> IDL&gt; print,mean(B)<br /> NaN<br /> IDL&gt; print,mean(B,/NAN)<br /> 1.50000</div>

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