filter1d: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/filter1d - from package: GMT

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/gmt/bin/filter1d - from package: GMT

You may install the required package with command apt-get install {package}

Error in other languages:
filter1d: bevel nie gevind nie
filter1d: comandă negăsită
filter1d: comando não encontrado
filter1d: commande introuvable
filter1d: command not found
filter1d: käsku ei ole
filter1d: không tìm thấy lệnh
filter1d: komanda nerasta
filter1d: Kommando nicht gefunden.
filter1d: kommandot finns inte
filter1d: komut yok
filter1d: nie znaleziono polecenia
filter1d: níor aimsíodh an t-ordú
filter1d: no se encontró la orden
filter1d: no s'ha trobat l'ordre
filter1d: opdracht niet gevonden
filter1d: parancs nem található
filter1d: perintah tidak ditemukan
filter1d: príkaz nenájdený
filter1d: příkaz nenalezen
filter1d: команда не найдена
filter1d: командата не е открита
filter1d: 命令找不到
filter1d: コマンドが見つかりません