[Nick Cox]

I have looked at your data again. As far as I can see it's still true that there is nothing in #11 that can be used for interpolation for firm_month1 == 2.

. l abc if firm_month1 == 2

     +-----+
     | abc |
     |-----|
 76. |   . |
 77. |   . |
 78. |   . |
 79. |   . |
 80. |   . |
     |-----|
 81. |   . |
 82. |   . |
 83. |   . |
 84. |   . |
 85. |   . |
     |-----|
 86. |   . |
 87. |   . |
 88. |   . |
 89. |   . |
 90. |   . |
     |-----|
 91. |   . |
 92. |   . |
 93. |   . |
 94. |   . |
 95. |   . |
     |-----|
 96. |   . |
 97. |   . |
 98. |   . |
 99. |   . |
100. |   . |
     +-----+

And naturally I can check nothing to do with 3, 4, 5.

Sorry, but I can't comment further without a reproducible example.

Otherwise no interpolation method of concern here can do anything if all values are missing.

Just to add to your problems, it's a kind of holiday weekend in Britain where I am and my activity on Statalist is likely to be intermittent at best.

[Luca Manzoni]

I have a similar question, can someone help me?
https://www.statalist.org/forums/for...-to-halfyearly

Thank you in advance.